To start learning to drive a car on the roads within the United Kingdom you must have , a valid and signed provisional driving licence and be of the correct age.To obtain one of these you can apply by filling out a form (D1) which can be obtained at most post offices

There are some requirements you need  before you are granted a licence.
You should have a good eyesight and be able to read a standard UK number plate from a distance of 20.5 metres (67 feet). If you cant then have your eyesight checked at an opticians. If you have to wear glasses or contact lenses this have to be declared on the form and you will have to wear them whenever you drive. 

To drive a car on a provisional licence you must be accompanied by a person in the passenger seat who has held a full UK car licence for at least 3 years. 

For more information you can obtain form D100 from most major post offices.You can write to:- DVLA, Swansea SA6 7JL or telephone 0870-240-0009