Do you mean you want to join one of the covens here on Spells of Magic? If so, take a look at the descriptions of the Covens (under Groups) on here until you find one you want to join, then follow the instructions to join that group.
If you are looking to join a real-life coven or group, here is a site with links to some groups in Germany: https://www.mandragoramagika.com/germany
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