I'm gonna try and play this guy close to comic canon, but I plan on deviating a little to add my own touch. 

[b]Name:[/b] James Buchanan "Bucky" Barnes 
[b]Alias:[/b] Captain America
[b]Age:[/b] Technically somewhere in his 90s, maybe even 100s. But psychically speaking, he's around 30 something. 
[b]Gender:[/b] Male

[b]Personality:[/b] James was standoffish to idea of training a bunch of snot nosed brats. First off, he's not overly fond of kids. Second, he suffers serious PTSD, and believes himself to be a ticking time bomb. However, Steve Rodgers and the rest of the Avengers (and SHIELD) had faith and encouragement in him. So, begrudgingly, he agreed. 

James holds most people at arms length, refusing to let himself get close. The few exceptions being the Avengers, who helped him through his rehab and whom he eventually fought beside. He's coarse, stoic, and at first, not very patient with his students. He quickly earns himself a reputation for being 'that asshole teacher who assigns extra homework because he can'. It's clear that he's not too enthusiastic about being there, and the only reason he stays is because he's seeking some kind of redemption for the whole "Winter Soldier" thing.
However, after a few weeks at the camp, (in between missions and mayhem), James finally starts to find that the kids are growing on him. With each new batch, he returns to his hardass teaching methods, but it doesn't take as long for him to warm up to them. One has to wonder, who's teaching who?

[b]Abilities:[/b] (copy and pasted from the wiki page)

Having trained under Steve Rogers (the original Captain America in World War II) and others in the time leading up to World War II, "Bucky" Barnes is a master of hand-to-hand combat and martial arts, as well as being skilled in the use of military weapons such as firearms and grenades. He also used throwing knives on occasion and was a gifted advance scout. His time as the covert Soviet agent known as the Winter Soldier helped to further hone his skills, making him the equal to his predecessor in combat skills and an expert assassin and spy. He is also fluent in many languages, including English, Spanish, Portuguese, German, Russian, Latin, and Japanese. He can understand French.

Winter Soldier's left arm is a cybernetic prosthetic with superhuman strength and enhanced reaction time. The arm can function when not in contact with Barnes and can discharge bolts of electrical energy from its palm. The arm can discharge an EMP causing electronics to either shutdown or become useless. The use of Barnes' EMP is shown when Barnes uses it to shutdown a Nick Fury LMD and when he attempts to use it on Iron Man. The arm has a holographic function to disguise it as a flesh and blood arm.

As Captain America, he possesses the original, indestructible, vibranium alloy shield used by his predecessor, as well as a Kevlar/Nomex blend, shock-absorbing costume. He often carries several conventional weapons such as knives, guns - mostly a Colt 1911-A1 .45 and a P08 Luger - and grenades.

The reason he was chosen was his experience, while under Hydra, he trained several soldiers. They told him "it's pretty much the same thing, just without the killing."

[b]Other:[/b] Because of his PTSD, James often find himself losing control. He takes medication for it, but even the strongest prescription can't erase what Hydra did to him. To help him in his recovery, some of the Avengers insisted he get a therapy dog. James was stubbornly against it, because he was doing just fine and he didn't need some mutt following him around, until they brought the dog home one day. For a few weeks, he pretended that the golden lab was a nuisance, but the ruse didn't last long. The man and his dog became inseparable. The dog, Lehigh, came with him to the camp. 

[b]Appearance:[/b]
Out of costume:
[hider=Bucky Barnes]
[img]http://th04.deviantart.net/fs70/PRE/f/2014/139/d/8/bucky_face_sketch_by_unicatstudio-d7hrdos.jpg[/img][/hider]

In costume:
[hider=The New Captain America]
[img]http://static.comicvine.com/uploads/original/11113/111131174/3364694-captainamerica_50_cover.jpg[/img][/hider]

[b]History:[/b]

James lost his father early on in WW2. He was sort of adopted by the soldiers at Camp Lehigh as a mascot. There, he met Steve Rodgers, the original Captain America. After training and gaining experience as a soldier, Bucky became the Capt's sidekick. All was fine and dandy until a mission went south. Captain American and Bucky found themselves of an experimental drone plane, armed with a bomb. The bomb exploded while they were trying to disarm it, sending Captain America into the North Atlantic to be deep frozen, and Bucky to god knows where. 

Everyone presumed his dead when Captain America was found and unthawed. Little did they know that the Russians had found Bucky first. He was revived, all memory of his past lost, and given a new arm. They 'reprogrammed' him to be their own personal Cold War assassin, the Winter Soldier. He was incredibly successful as he traveled all across the globe, committing assassination and then disappearing like a ghost. However, because of his reprogrammed memories, he was unstable. To keep him from rebelling. Hydra kept him in cryo freeze. This allowed him to live on for 70 years, while only aging a few. 

It was 70 years later, after Captain America was thawed and brought back into action, that Bucky was discovered. While sent to assassinate the patriotic hero, Steve recognized his old best friend. SHIELD was eventually able to save him, bring back his old memories, and give him work to keep him busy. However, his identity had to be kept secret. The Winter Soldier's death was faked, so that Hydra wouldn't try to hunt him down. After Steve's supposed death and resignation, Bucky was talked into becoming Captain America. Only a select few SHIELD agents, and Avengers, know the true identity of this new Captain America, and if anyone else found out, they could all be in danger. 

It was with much persuasion that James agreed to come to the camp to train kids. SHIELD thought it would help him in his slow and steady recovery, and certainly help discipline the kids. James is careful to not let anyone see him without his mask, or to let his bionic arm show.