How to edit Gmod Dedicated Server options?

Okay so apparantly I fixed the problem on my previous thread with the error and the out of date Server issue. Now my question is how do I make it so my server’s gamemode is set to DarkRp? As well as setting the maxplayers, options, etc.?

You know how to make a startup?

Because, if you do, you’ll need to set these two into the commandline:
+sv_gamemode DarkRP +sv_defaultgamemode DarkRP

I tried both upper and lower case, it does not really care, both works.