Vincy, first off, you don't have to PM me the exact same question if you have already posted it here.
If you want your server to be on all day, you just... leave your computer on.
That's it.
You can host a server like one would always do, via the "Host server" menu, and just don't close the game for the rest of the day to have it run forever.
If you are going to have to close SRB2 for whatever reason but you still want the server running, you can try hosting a "Dedicated server". KaisoAri already gave you a link to the wiki about dedicated server hosting and other info.