To script a server, you'll need to learn the Squirrel programming language. After, you can use the functions, events, and server settings found here to make your own custom scripts:
http://www.liberty-unleashed.co.uk/LUWiki

The server itself comes with a basic, generic gamemode script that you can take a look at for an example. There are also multiple files in the server's root directory that control things such as manual blip placements, character spawn selection classes, and the like. These files can generally be viewed and edited using a standard text file editor like Notepad, or a similar third party application.

so how do i learn the squirrel programming language so i can add scripts?

So i'm new to making servers for this kind of game and program to make multiplayer. So if anyone can help me by telling me what to do to make a server. I already have the server downloaded so help is very much appreciated if anyone can. Also i would like to know how to add a new script because im wanting to add the script where it adds the blips on the map so i can find where i want to go so if anyone that knows how to do that would reply as well it would be appreciated as well.