Traditionally a Coven is a group of up to 13 people.
In inter-generational Satanic covens, as new family members come of age, the Coven swells to capacity then eventually divides in to separate covens as the numbers exceed 13.
Unless you happen to have been born into a Satanic family, you are unlikely to be invited to join a Coven like this.
Straight neo-Satanists, of course, form local Covens. They are very secretive, so again you will be unable to find out where they are, or how they meet. You will also need to join a mixed gender Coven. Again, not ideal for gay and some bisexual men.
I have come across men who are members of small gay covens. These tend to be located in big cities like London, New York, Berlin, Miami and Los Angeles. They do exist, but again they will be very discreet in their recruitment.
This will obviously be a group of many more men than 13, but will give those who are serious, and vetted, the opportunity to network and form local or virtual Covens.
You will also be able to use the resources of the site to set up, maintain and communicate with your Coven.