How do you start gta online after completing gta v story mode?

The verified evidence from Wikipedia focuses on the development history of Grand Theft Auto V, including its release dates, development teams, and marketing strategies. It does not discuss gameplay mechanics, post-story mode features, or the process of accessing GTA Online. To start GTA Online after completing story mode, players typically need to access the online mode through the game's main menu or character selection screen, but this specific information is not present in the provided source.