She's already remembered how Junketsu was first activated, actually!

Beyond that first time of feeding it blood to activate it, it still requires blood to function at an other time - Junketsu has a set of clasps on its sleeve that inject three needles into his wearer to draw that blood. That's more of a thing that wouldn't be hard to figure out on one's own later on.

Beyond that, she's remembered the scene where Satsuki first donned Junketsu, so she knows how it works. (And thus why she's been able to be so cocky towards Raye without any powers.)