Hi Kaosk,
Outboard motors use a 'dog clutch' in the gearcase which will only shift if the 'dogs' align. If the motor is not running, you may have to turn(wiggle back and forth) the prop some to align the dog teeth to allow the clutch dogs to shift into forward or reverse. Outboard motors should NOT be shifted when not running, except if you are turning the prop!!
Normally, if you pull the choke knob 'out', that closes the choke butterfly for starting. When the choke knob is pushed 'in', the choke butterfly is 'open' for running.
The throttle control usually has a 'start' position which is a little up from the idle position and the throttle should be set there for starting.
Before starting, squeeze the primer bulb on the fuel line till the bulb is firm to pump fuel into the carb.
Motors which will run only with the choke 'on'(knob pulled out) or 'partly on' usually have a fuel restriction or fuel flow problem. Could be in the carb. Could be the fuel line connector is loose or not seated.
On modern outboards, there is a 'stop switch'. It could be where the safety lanyard clips on, check your owners manual. While boating, stop the outboard with the switch, not by pulling the choke out, which could flood the motor. When thru boating for the day, its good practice to start the motor, disconnect the fuel hose, and idle the motor(in the water or on a flusher) till it uses up the fuel in the carb and stops.
Be sure to read the owners manual for the correct procedures to follow for YOUR motor!
A new motor should be under warranty. and the dealer should help you with problems like this. You could ask the dealer to start and run the motor in their test tank. Watch the mechanic start and run the motor, and make a list of his starting procedures, then start the motor yourself, with the mechanic watching.
I hope this info helps!