Two things:
The rotation code should be in the actual BP rather than where you are spawning it … OO code and all that …
Rotating the character requires you to get the current character and add a rotator value to that, times the delta , which you can get from the event tick. I dont have the editor installed on my work machine so cant provide screenshots. You also might want to consider a speed float so you can vary it, which would be times the delta .
A basic version can be seen here:
You can also add a rotating component to the actor if you want the simple approach: