Do this:
Everything is described in this article on the wiki:
Getting a Rikidar Authenticator account
TL;DR
This forum uses SSO (Single Sign-on) through Rikidar Authenticator (which is a self-hosted and encrypted PocketID server). You can then use that account to log in anywhere in the network.
Other Relevant Articles
If you'd like to read more about Rikidar Authenticator, read this page: Rikidar Authenticator
The whole wiki is useful: Rikidar Wki