If you want just to display a debug message, you can use the PrintString function inside an actor when the EventBeginOverlap is triggered. If you want something a bit more elaborate, you will need to create a widget, add some text to it and set it to visible when the character enters the trigger.
Here you have an example. You can ignore the Cast to box that is used there Video example
I want to make that when entering a trigger a text is shown on the screen, that is cast only 1 time and after a few seconds the trigger is destroyed, something like that in unity but in unreal I have no idea how to do it, I do not know if there is another way but it would help me a lot to know how to do it (sorry if the English is a little bad, I wrote it with the translator).