Joining a pack

I've read this on the site but I just want to be sure. When making an attempt to join a pack, you post on their territory at the borders and wait for the leader correct? For example if I want to join Salsola I go to their thread page and post there at their borders?

Yes, generally this is how you'll do it! However, Salsola has a slightly more involved joining process; it is encouraged that prospective joiners befriend a Salsolan to learn about the pack, and that they bring a gift when they join. Salsola's joining policies can be found on their website!