Hi, Firstly if the wall is bare to the brick work, make sure that the wall is dust free and dry.
Best use plasterboards 2400x1200 they come in different thickness, you should be okay using any as long as all the same and you'll need plasterboard adhesive.
Mark on the wall where you intend to put your first board by drawing a chalk line from ceiling to floor, then the second and so on. This will help you when you put board adhesive on to wall.
Mix board adhesive with clean water in a bucket or tub. Water in first. When mixed you want it to be a nice creamy mix not to wet or dry, if you can put it on your trowel with out it falling off, that,s good. You can either put board adhesive on to board or wall. About trowel full evenly spaced out (every 10 inch to a foot) on edge of board and across middle of board too. Then put board on wall, taping so adhesive with bond to wall and board. Use spirt level and a straight edge to keep everything straight and level. Then repeat, board by board.
Hope this info usefull and understandable, little hard to explain without being there or using pictures.