The Login button is the Grey Button in the top left hand corner of the screen, if you are already logged in it will show you name instead. There is a guide to help here.
Click the Login Button, and then click the Forgot My Password link and we will send you a new password by email, you can then change that to something you can remember
Your membership number can be found on your profile page, after you have logged in click on your name in the top left hand corner, you may need to scroll down the page to show the Membership number field