You must port forward 25565 on your router, When you have done that download a Minecraft Classic Server Software, Then just edit the proprieties which is a notepad file, This has all the names, Settings and loads of stuff to change, Once you have done that you should run your Server and then it should work, You can also edit ranks and other stuff in server proprieties which can be opened VIA the console.

Note: You can get help on port forwarding your router here.

Well, Not every software has cpature the flag, You will need to find a spesific software with that command/game, I don't have a server anymore so you will have to look around on what software's have capture the flag.

A few software's that are pretty good are,

- MCLawl

- MCZall

- 800Craft

There are more but you would have to go on google or youtube and find out.