Before I start this post there’s a detailed explanation given on NHS website, please follow the link
My brief version 
- Find a Surgery (Clinic in Indian Terms) closer to your home.
https://www.google.com/maps/search/surgery/ - An address proof (mostly Rental Agreement with BRP)
a. Sometimes they accept Bonafide Letter from your company. Ask your HR - Download and Fill the attached form.
- Go to the surgery (1) with the address proof, take the family too (BRP must for all).
- That’s it.