If you know your buddy's username, this will be an easy way to add him to your game:
- Go to your game.
- Go to your "GM Menu"
- Go to "Edit Players" (top link)
- Select "Add (Wizard)" (top button)
- In the box where it says "If you wish to assign a new character" type in anything for now. You can change a character's name later. If you already know the character's name (not the player's username) enter it here, otherwise put in something like Character1.
- In next box below, type in your buddy's Username and click the "Continue Adding - Search" button
- In the next menu, check the "1" box next to the new Character' name, and then click the "Add This Player" button at the bottom right.
After your buddy is added to your game, you can go back into the GM Menue and edit his character's name, etc.
There's a bit of a learning curve for the GM's Menu, but once you get him added, the Help Files can walk you through all the other options.
Good luck!