Connect a channel
Once per channel, not per listing — connections belong to your user account, and what "needs attention" means when one shows it.
Open Account → Social connections. Each platform is its own card, showing what you have connected and letting you add another.

You do this once per channel, not once per listing. Connections belong to your user account rather than to one workspace, so if you operate several you can use the same channels across all of them.
A connection can show as needing attention. That means the platform revoked our access — usually because a password changed, an admin removed the app, or the platform expired the token on its own schedule. Reconnecting takes a few seconds and nothing else is affected; scheduled posts waiting on that channel will go out once it is healthy again.