How to mount a large TV onto plasterboard/drywall studwork, using a full motion cantilever TV wall bracket
It is very important to use a bracket with a large rectangular base plate. The dimensions of the baseplate are usually 480mm length 240mm width or thereabouts.

Do not use the type of bracket with a narrow vertical type of base plate:

Plasterboard/drywall is installed onto a wooden/metal framework. The vertical studwork is usually centred at 400mm 450mm 500mm or 600mm, most commonly 500mm centres. Use a stud finder device to find the centres.
When using a 480mm x 200mm baseplate the chances are that you will be able to get a fix into one of the vertical studs. You can adapt the baseplate if required. If there isn’t a fixing hole in the baseplate which falls in line with the vertical stud, simply drill a hole in the baseplate to match.
For the other fixing points use GeeFix cavity wall fixings. Position the backplate/anchor in the cavity either vertically or at a 45degree angle or thereabouts. The screws provided in the pack will be strong enough for your installation, just use metal washers on the screws to suit your bracket fixing points
GeeFix Ltd