Installing a custom Garry's Mod map

Step 1. Locate where you'd want to download your map from. This can be either from the Steam workshop or GarrysMods.org
(You'll notice inside the files of the map you'll be looking for a (.bsp file)
Step 2. Download the files to your local PC.
(Make sure to store it somewhere you can find it)
Step 3. Once at that location, upload/download the BSP file you wish to use. It will look something like this "RP_Anaxes.bsp".
[NOTE: You will want to use the BSP Name, not the workshop ID or Name]
Step 4. Once you've found your bsp file, navigate back to your FTP client and connect to your server. Upload your .bsp file to your /garrysmod/garrysmod/maps/ on your server.
[How to use your FTP Client]
Step 5. After uploading your .bsp file to your files, navigate to your Command-Line on your control panel. (Create a Custom Commandline if you don't have one already)
Step 6. Underneath the "Startup Map" setting insert your .bsp file name. Example: "RP_Anaxes".
[NOTE: Do not put .bsp in the name of the startup name. It will only need to be the name of the map, not the file name if your map name says "rp_anaxes.bsp" it only needs to be setup as "rp_anaxes"]
Step: 7. Select your command line after you save your settings and inserted the map you want to use into the Startup Map parameter.
Step 8. Start your server! Your map should be all setup 

If you have any further questions or concerns, please submit a ticket to our game server support team found here:
Game Server Technical Support