Blueprint to swap materials when player click on the mesh in-game, don't know what I've done wrong

Hi everyone,

I’ve followed an example on how to set this up, well I basically copied a screenshot (so that’s why I’m thinking there may be more behind the scenes stuff that I don’t know how to do)

Anyway I have two materials for a monitor - how it looks on and how it looks when it’s off. I would like to be able to swap these around in game, so essentially the player is clicking to turn the screen on and off.

Here’s what I have so far.

Thank you guys!