The maps.ini file in your addons\amx\config folder contains a list of maps that can be chosen from the Changelevel Menu using the amx_mapmenu command. This is what the default maps.ini looks like:
(Note that a semi-colon ; was inserted at the beginning of some lines. This prevents them from being used.)
Adding maps to the menu for use is very simple and should be entered just as other maps are in this file. The map name first without the .bsp extension then an optional brief description "in quotes". So if you wanted to add the map fy_snow.bsp to your maps.ini file it would look like this:
To remove the map, simply remove the line containing the map name from the file, or insert a semi-colon at the beginning of the line. The semi-colon ";" causes that line to be ignored.
This menu is accessed in the game by typing amx_mapmenu in the console. Or by binding a key to that command. The menu will show up on the left side of your screen while playing. It looks like this:
Just select the number in front of the map to change it and that's it! If you have more than eight maps, option 9. will show you them. Option 0. takes you to the previous page.
Any changes made to the maps.ini file will show up after the next map change or server restart.