them little screws ain't gonna hold shit
right then, find the studs
and, if you need to, remove the plasterboard to locate them
use lots of fixings, more than you'll need, because the last thing you want is for it to drop on the floor
i used 12 M8 raw bolts to hold my 42" plasma bracket into solid brickwork
i used 6 M12 raw bolts to hold my 50" plasma
trust me, the plasterboard wall is no way going to take 50+ kgs on some little screws, they are for hanging small pictures up with from the looks of them
if you want to mount to the solid wall behind, you can use some dpm but you'll need to inslute the whole section you are going to fix too otherwise, as stated above, you are going to have a damp issue sooner or later
best option would be to probably fix through the studs and then tie into that to be extra secure
it also depends on the bracket you buy as to how many holes you get, if your bracket is to be used in congunction with some M12 bolts then the holes are going to be massivly larger than them piddly little screw heads
if in doubt, ask an expert who will give you the correct advice after surveying the properlty