Edit Your L2.Ini and add your ip where it says "ServerAdr= bla bla bla" Where its bla bla bla add your own address, then send the L2.InI file to your friend, And tell him to put the l2.ini to LineageII/System/ , If it asks to copy and replace, press Ok ;) Then Launch L2.exe from the system folder and Your done, By the way, Configure your server settings so it will be auto create accounts ;] Good Luck and Have Fun!
Oh yeah, edit your l2.ini With L2FileEdit