Not a member message when making a post
When you see a message saying that you need to join the town, it means that the town moderators have not yet approved your membership. Please go to your My Towns page here: https://www.freecycle.org/home/my-towns/ to see if there is a note saying your membership is awaiting approval.
If it is, and you want to check with the moderators about when it will be approved, you can send them a message to ask about the status of your membership.