All she had to do was feed mana to the circle? Hopefully, Toshiko would get around to some explanation of the design at a later point; knowing how to use a spell but having no idea what it was--or how to tell it apart from something of similar operation but vastly more danger--seemed to be a rather big risk to take. 

So, place the ofuda in the circle--a quick flick of her wrist was enough to pull the shred of paper from Toshiko's fingers and allow it to float into position--and then feed mana to it. Repeat the same visualisation exercise from earlier, her fingers forming a bridge for mana to be sucked down into the circle. The circle that, in its own way, knew more about what was going on than the apprentice herself did...

Hopefully, this worked in a manner she could make sense of the results.