I am brand new to UE4 and have some questions. I’m trying to create a FPS game based off the UE4.27 sample game. So the question is, exactly how do I integrate an environment I downloaded from the marketplace for example? Or other stuff like guns, etc? Thanks!
When you say environment I suppose you mean the level or map, somewhere in that project the map is stored, find it, and use right click - migrate and send that asset to your new project. Inside your new project, in the project settings - maps and modes, set your project to use your migrated map, save and reopen project and map should be there. You say guns and weapons, that also should be things you can migrate like meshes and BPs and animations and things.