Turn off your power supply. Do not attempt the installation, until you are sure that the supply is off. Review the manufacturer's installation instructions and safety guidelines.
Find the studs in the wall using a stud detector. If there is not a stud in the exact location you want to position the heater, use a wall anchor socket.
Install the wall bracket. Position the bracket so that the heater will cover the wires protruding from the wall. The heater should be at least seven inches from the floor. You will need a spirit level to draw a straight, horizontal line with a pencil or piece of chalk. Hold the bracket up to the wall and ensure that the bracket is in line with the line you drew. Mark where the screw holes are.
In newly constructed homes, wires are often left protruding from the walls for such installations. If the wires are not evident, you will need to use a stud finder with a wire mode to help you locate the wires. Once you have located the position of the wires, gently break through the drywall until you can see the wires. You will ideally need a hole big enough to allow you to fit your fingers in easily to work on the wires. You must be very careful not to damage the wires as you break through and it is better to work slowly and carefully..
Pull the wires out of the wall at least four inches. Open the plate on the rear of the heater and ease those wires out. Connect the color coded wires in accordance with the manufacturer's instructions. Use wire nuts on your connections, this is preferable to using insulation tape. Wire nuts will probably be included with the heater, but, if not, they can be purchased cheaply at a home supplies store. The wires on the heater should be clearly marked and the instructions should make it clear which wire is to be connected to which, but, if you are in any doubt, do not continue with the installation and consult an electrician.
Hang the heater on the bracket.
Install the thermostat on the wall, if it is separate to the heater unit. The thermostat should be located away from the heater but exposed to the room's general airflow. The small thermostat will generally come with a mounting bracket. This is, essentially, a much smaller version of the heater's bracket. Use your spirit level to make sure that you mount the bracket straight, and then attach the thermostat to it.
Test the heater.