You mean like the HUD blueprint class? Or do you have some other blueprint (like a widget of some sort) that you are using as your HUD?
In order to get an event out of a HUD blueprint class when you are in your character, you need to use the Get Player Controller node → Get HUD node → Cast to (the name of your HUD here) → pull off the pin of the cast and there should be an option to call your event.
However, it should be noted that use of a HUD type blueprint is a bit outdated and most people just use widgets instead now.