This is a very vague question. But I think what you need to do generally speaking is get a reference to wherever you are spawning your “projectiles” or bullets or whatever is being “shot” and when you press that button, you are going to want to have a custom event or function in the firing BP that is going to get called from the widget by using the “On Clicked” event for the button. So like this:
In widget BP:
- On Clicked → Get Reference To Character/Firing BP
- Call function/event to fire projectile
In Character/Firing BP
- Create custom event/function that spawns a projectile (Spawn Actor From Class Node)
If you are just starting out these tutorials may be helpful to you: