You're 17+ and you want to get driving on the road. Unless you're the Queen (who is the only person in the country not to have one to drive or even require number plates on any car that she owns), then you're going to have to apply for your provisional car driving licence! You can't apply for any driving tests or start driving on the road with World Driving without one!
Applying for your provisional driving licence can be done online if you:
are a resident of Great Britain
can meet the minimum age requirement
can meet the minimum eyesight requirement
are currently not prevented from driving for any reason
can pay by MasterCard, Visa, Electron or Delta debit or credit card
have a valid UK passport or another form of identity
can provide addresses of where you have lived over the last three years
If you cannot apply online then you will need to go to the Post Office or go the DVLA website to obtain a D1 application form. The DVLA can also be contacted by phoning 0300 790 6801.
Once you have received your form and completed it, you must also provide some identity documents confirming who you are (i.e. passport, birth certificate etc.) and a passport-type size colour photograph taken against a plain light background. You can then send your completed form, documents and fee to the DVLA. If you're uneasy about sending identity documents through the post then there is a premium form checking service available at selected Post Offices for an extra fee.