For a general overview of setting up and navigating the game's basics before jumping into a multiplayer session, check out this guide:

Playing a "cracked" or portable version of in multiplayer typically requires using LAN-emulation software or specific Steamworks fixes, as the game's official multiplayer is tied to the Steam "multiplayer_test" beta branch. Methods for Cracked Multiplayer

Multiplayer in The Long Drive is notoriously buggy, even in the official version.