Assuming you've chosen a supervisor... you should say when and where you graduated from and with what degree(s), what the project would be (or at least the area), and that based on their previous publications, you thought it might be a project they'd be interested in supervising. You should be sending an email though, not sure if you meant to say that. Another option which could be available is to outline a project proposal and ask the relevant departmental secretary to send it to staff, then the ones who are interested in supervising it could contact you.