There is a link on the coven's front page, labeled "Accepting Applications."
The information they require, also from their front page:
Divine Essence Application: Please mail the Priest Tadashi your application We check profiles before you join, so please have a profile picture (if not then please say why you can't) your age and something in your bio. Big or small, just keep it clean.
How long have you been studying and practicing magick?
What topics are you most knowledgeable about?
What topics do you need help with?
Have you been in any other coven on SoM? If so, which ones?
Have you been in any other coven outside of SoM?
What are you going to contribute to the coven?
What are you expecting to learn from this coven?
So it seems you should either mail the application to Tadashi, or click the application link.