As for the coven. That depe day on what you want to learn. Different covens teach different subjects. And then you have to be sure you meet the requirements for the coven when applying. Generally the covens tell you what requirements to meet in their description. If there are none then it's likely all you have to do is cluck the application link and wait for the high priest(essay) to accept you.
Every one has the ability to do magick dear. It's a matter of where your belief is, what your intend.t is, how well you understand what magick is and how well you can control energy.
Your powers and your ability to do magick rests with you. Only you can answer what your powers are.
As for your question on element. You can do some meditations to find out. Work with each element to see what you're best at or pick up fastest. You may already know what your element is.
If you would like more elaborations on any of this send me a message and I will further help you.