Signing up to sports clubs is easy, all you need to do is log in to essexstudent.com (sign up here if you haven't already) and then click through onto the sports team page you'd like to join.
Before joining a sports team you will need to buy sports fed membership, this costs £10 for the year which covers your insurance to play the sports. You are then an official member and are allowed to participate in league competitions with other universities, once you've joined you can join as many sports teams as you like.
If you are not a student you will need to buy the associate membership first. This costs £10.