If the corner of edge of your wall is not 90-degrees, you will need to measure that angle with an angle measuring tool and cut your moulding to fit that angle. It will be a compound cut, with one cut on the face of the moulding, and one on the edge. If you are adding a new colour to the wall, or a dark colour, you may want to do a coat of paint to both the wall and mouldings before you nail anything to the wall. It will still require a second coat after nailing mouldings up. When a piece is ready to place on the wall, check that your angles are correct (you can do this with a speed square for 45-degree or 90-degree angles), and nail the moulding to the wall with a cordless nail gun. Use a stud finder to mark the studs behind the wall and try to get your nails into as many studs as possible while putting up boards. Use drywall compound to fill any nail holes or gaps between mouldings.