Am not sure about exchanging the licence but for the test first of all there is no parallel parking test
You can go to RAYA driving school and go the police officer first with the form and all required documents and try to exchange your license if not he will sign the form for you to do the test directly.
You should do this first because the school will till that you need to take 10 lessons course

You will start at 5:30 with the theoretical (signs exam) they will ask not more than 5-6 signs if you answered with confidence and quickly.
THE DRIVING SCHOOL HAVE A SMALL BOOKLET that has around 30 signs

Then they will let you know if you pass if yes you go out to start the practical exam:
1) Is the hill test , you have to stop in the middle (on the line painted in the street) then continue till the end of it, then reverse back to you starting point , which means you have to reverse as L shape
2) Then you go to the parking test, you have to do it in one shot and make sure not to cross the lines or hit the, and you have to reverse back from the parking position.
3) After a while they will let you know if you pass and if yes they will call your name so you in the bus and start follow the test car.
4) When you fell that you are ready and you want to go next and when the bus stops go out and go to the car and start with the seat belt then the mirror and start driving smoothly as you used to do, don’t think of it as an exam.
You can search in qatarliving and you will find many answers
GOOD LUCK