Could someone please explain how maps work

I’m really confused at how the maps in gmod work when they are uploaded to a server. I uploaded ttt_clue.bsp to my server and I can load it but for anyone else it says missing maps ttt_clue.bsp. How do I get it to install properly?

You need to own a FastDL web server so you can host the map for download.

I got it up working but it says it is bigger than 16mb so it’s too big to download