Patching GTAIV to work on GTA Connected

The following instructions only apply to a Default GTAIV Directory. If you're using a Modded Directory, don't expect GTA Connected to function properly.

It is recommended to use The Complete Edition, since it includes every Episode in one directory so you will be able to switch between Episodes and join any Server without issues

Instructions

Download the patch for either 1.0.8.0 or 1.0.7.0. (1.0.8.0 is recommended)
Unzip it. it should make a folder called Retail.
Drag the Retail folder into your GTAIV Directory. Don't move the files out of the folder! Just move the whole folder itself.
Open the GTA Connected launcher and select Tools > Game Settings. Choose Grand Theft Auto IV from the Game dropdown list.
Next to "Game EXE Path", click the Browse button to set the path for the exe to GTAIV.exe inside the new Retail folder in your GTAIV directory:

(Default Steam Path: "...steamapps\common\Grand Theft Auto IV\GTAIV\Retail\GTAIV.exe")

Select Tools > Launcher Settings and type a Name for yourself
Double-click on a Server to connect to it

How To Join Lobbies

Press UP key to bring up phone
Go down and press Multiplayer
Press Custom Match to see any active lobbies. Join by double-clicking Lobby
If you know what Lobby is currently being played (e.g. through holding TAB if the server includes v-scoreboard), you can directly connect to a Lobby through QuickMatch on the phone

Note

If you've followed those instructions correctly, the original files should be intact and unmodified. This means Steam/Rockstar Launcher won't force the files to be reverted, and you can play GTAIV on GTA Connected and also play the original GTAIV through Steam/Rockstar Launcher