Hi queenofdirt, thanks for playing The Arcade Tower, I’m glad you love it ! I’m sorry you’re stuck there !
In this level, to activate the pressure plate, you need to simply throw an arrow using your bow into the plate. There is also a tutorial box showing up at the bottom of the screen when you walk nearby saying that “Pressure plates can be activated with arrows”. Here’s a screenshot of what you should do :
I hope it answers your problem. Good luck with the rest of the game !