Need help with how to use the Craigslist forum (Granada Hills)

I don't understand how to use Craigslist forum to create a new thread, what URL I'm supposed to use, what is my handle etc.
When I click on: "Compose new thread" I get this: "this forum requires a craigslist account and a forums handle for that account.
" Where do I go from here? I have a Craigslist account.
I don't know what my handle is, but I had one a few years back.