There are no special requirements when you register with a GP on a T5 visa.
Your GP should be local to you and where you live, so the only thing that is required is a proof of address. You can register online or in person. To start the process you can register online here: How to register with a GP surgery – https://www.nhs.uk/nhs-services/gps/how-to-register-with-a-gp-surgery/