Hi, I am 21yo french guy, and i've already make a lot of sa:mp servers, even script the GameMode in pawnoo, so, I think I could help you with that, and in the same time, explain you what to do after the installation of the server, and how to manage yours.
Basically, there's two kind of SAMP server, by ftp, or database, and then, you need to choose which gamemode you'd like to see on your server.