To play with friends, open up ide.exe and select the "start server" tab
Near the bottom right corner you will see a "saved configuations" box
Click on one and press load then START server to get things rolling.

You will of course notice there are pletny of other options to mess with before starting the server.
Like Gravity or the instagib modifier, or if you want to play an entererly diffrent game, I have a few selectable from the IWAD tab

After all that jazz just flip over to the servers tab and join your own server(your friend should be able to as well)

Hopefully this all works for you, if not go bug ReMixx, I am no tech wizard unfortunately :p