This was a huge problem in GTA 4 to consumers. The idea of multiplayer was not clearly visible. All that is needed to join multiplayer is the phone. On the phone there is a free play selection. Click it and you shall start the game.
Chat with our AI personalities
you need to have a psn account then get some friends that have an account too add them and tell them if they have gta iv then in gta iv get your cellphone out and scroll down and you will find multiplayer option :) hope i helped p.s if it is on xbox360 then idk i don't have xbox i have ps3 slim anyone welcome to add i have gta and we can play home add me. alexis522 ;)
download and install online pakx.exe
http://elypter.net84.net/gta2.tk/packs.html#onlinep
and READ the instructions