If you are referring to this site, I believe that no new covens will be created. There are several Covens that are in need of new leadership. You are able to apply to take over those covens if you are a member in good standing with an account that is 3 months old. There is a place to apply to them on the coven page.
If you mean in your physical area, you will need to find several like minded people and get them all to agree to form a coven. Than there is the process of deciding how things will be run and by who.
Covens, weither on line or in person, take a lot of work and guidance. They are not always easy. Covens require a few knowledgeable people to run them.
A study group may serve as the early phase of a coven if all the members are new to the path.