You need to add that UMG widget (one blueprint with logo) to player controller (or used pawn) camera.
Best it would be if you watched simple umg tutorial.
Stuff you need is described here: 4. Scripting the Main Menu | Unreal Engine Documentation
steps 18 and 19.
But look at everything in that tutorial, soon you probably will want to make some key shortcut to hide and show logo etc.