Before I begin with the above let me tell you driving on the left-hand side as well as the traffic conditions in this city can be horrific. One piece of advice is to take a driving course even if you are not going to take a driving test. This will climatize you to driving on the wrong side of the road as well as giving you invaluable experience.
Driving in Istanbul-Getting your Driving License

I chose to buy an old car which I aptly named “cesur” which means brave- and let me tell you he was before purchasing a better car!
Now regarding to the laws about applying for and getting granted a Turkish driving license you have two options.
Take a driving course and then take a driving test (which includes a written exam)
Use your foreign license which you can to do for year but in order to do so you will have to leave Turkey once to show you are visiting.
The procedure I opted for was to hand in my English driver’s license and get back a Turkish version. It is a tricky amount of paperwork so for help contact us on Expats in Istanbul.