Basically, the widget will set a variable which is a blueprint class. The class of you pawn.
Typically, it would be useful to have that variable somewhere more accessible, like in the game instance. So, you can keep it there.
Somehow then, there are many ways, you need to start your levels ‘pawnless’, take a look in the game instance, spawn and posses the right kind of pawn.
Assuming you’re using OpenLevel, a logical place to do this would be the level blueprint. On begin play, the level BP opens the game instance, grabs the pawn type, spawns it, and makes sure you posses it.