You can apply for your provisional licence three months before your 17th Birthday. You need to say on the application form, the class of vehicle that you wish to drive. You can apply online or by post. The cost is currently £50.
If you have a provisional licence to drive a car (catB) then you are allowed to drive a car under the supervision of a full licence holder who has held a full driving licence for at least 3 years and is aged 21 or over. The supervising driver needs to sit in the front seat of the car.
Once you have passed your test you need to apply for your full driving licence within two years.