Just had the impellor changed by a marine mechanic and said it is fine, but when got home it started fist time then cut out and now wont start. I am completely new to outboards and there is a choke on this. Am l simply starting it wrong or anything else...please help!

is their any fuel in the in the tank and if so check the fuel filter and the fuel pipes, there is a choke make sure it is not on otherwise you will just gas up the system

First put some ear muffs on it and turn the hose on.
Check that there is fuel in the tank.
Check that the fuel is turned ON.
Close the choke.
Set throttle to START (about 1/4 throttle)

Pull cord firmly. It should fire up.
If it doesn't: check spark plug cable is connected.

Pull it again. and again and again...