There isn't necessarily anything that you need to do to "join"; It's more like "how to 'integrate' yourself into the fandom".
As someone who is still relatively new to the fandom, i would say to start off by making a FurAffinity account, then browse and do things on the forums which interest you.
Besides that, searching various "furry" subjects on youtube and google that interest you(ie "furry soldier" for me); and talking to some people who have been in the fandom for a couple of years about [insert subject here] will also introduce you to even more furry fun!
I hope i've helped.
and Welcome to the Club! [link]