Help on using prefabs

Hello everyone! Was hoping to get some guidance or for someone to tell me I am brain dead.
I’m having such a difficult time with these prefabs that are now in the in game mod browser. I can’t seem to get them to work? When I download a mod, it will show up and allow me to apply it to my world, however if I download a prefab, I can’t see it anywhere when I click on my word but I can see it in my “downloaded mods” section.
Previously I added a file before the in game mod browser was a thing to try prefabs from places like nexus and couldn’t figure that out either. Not sure if that has anything to do with them not working now. Also, I created an “asset” which I don’t know where I did that but it now shows up when I click on a world.
If anyone has any advice or a good tutorial on how to use prefabs I’d appreciate it!