To begin the learning process on the road you would normally need to need to be at least 17 years old, be able to read a current style UK number plate of any car from a minimum distance of 20m and have a provisional driving licence by law.
You can apply for a licence up to 3 months before your 17th birthday, but cannot take lessons on the public roads, or take a Theory Test until your birthday.
Your Provisional Licence - You can apply online for a comprehensive pack containing everything you need , or get an application form at the Post Office.
The cost of a provisional driving licence is currently £34 for online applications (06/2020). You will normally receive your licence in a week to ten days.
More useful information - here