Put Level in outliner (NOT Level Instance)

I’m picking up where a friend of mine left off in a project and can’t figure out how he got the levels to display as “Level” in the outliner. I tried to drag my new level (LVL_World_C) into the viewport, but that just created a level instance with an error message. I also tried changing the streaming method for World_C, but neither Blueprint nor Always Loaded worked. How do I get World_C into the world as Level rather than Level Instance?