If you are new to the area and would like to join the Practice, you can simply ask at Reception. It would help to have your medical card, but it is not necessary. You will be given forms to fill in and sign.
Your medical records from your previous GP will follow in due course.
If you are not a UK citizen your passport is required for proof of identity.
For more information:
TheSite - a health website designed specifically for teenagers and under 24's - Information on registering with a GP
NHS Choices - Information on registering with a GP