If you own a Rocket League account, you must connect your Steam Account in your PlayVS profile. Complete the following steps to do so:
If you do not already own a Rocket League account, PlayVS will provide one for you. On Game Day, you will see your assigned username and password from the connections panel to log in. You will need to request an account in your Player Dashboard.
Steam Username and Password. Users may not change the the Steam username or password.
Purchase Power. Users do not have purchase power for Steam accounts. This includes installing free or purchased games in Steam or purchasing Rocket League enhancements, (i.e. car packs, skins, or keys).