first you have to find your internal IP address, if you have a router.
go to Run type in cmd, then type in ipconfig
it should look like this



you see the part that says 192.168.1.102
just remember the last 3 digits of that

then go into Internet explorer or Firefox or whatever browser you use, type 192.168.1.1 into the address bar, press enter, you will be asked for a username and password, just type in admin for the password and you will get in.

now click the Security button and uncheck all the boxes in there, click Save Settings
then go to the Applications & Gaming tab and make it look like this



then click Save Settings and exit that window

then tell your friends to add this to their servers.txt

your IP address from http://whatismyip.com followed by :20184

so it would look like this 67.345.67.8:20184