Inspect the house and count all the doors and windows since you will ideally need one sensor for each. You can place sensors only on the lower-level entry points to save money, but you then leave the second or third floor vulnerable to compromise. Decide where you want a main control panel, which should be near a main entrance and near a power source while not being visible from a window outside.
Buy a do-it-yourself security system that accommodates your needs by providing the number of sensors you are looking for. If you need more sensors than a system provides, order more individually. But they should be the same make and model if possible to avoid compatibility problems. Use a wireless system since they are much simpler to set up than a wired one. A wired system is more likely to require professional assistance.
Drill a hole in the wall where your control panel will be located. Drill a second hole under the electrical outlet that it will plug into. The outlet should not be light-switch controlled to prevent accidental system shutoff. Verify that the control panel power cable is long enough to connect the two holes.
Run the power cable through the wall and pull it out of the second hole so you can plug it into the outlet. The panel will sit over the first hole with the cable behind it so it is not visible.
Attach door and window sensors to each of the entryways that you want protected. The transmitter sticks to the frame of the door or window while a magnet attaches across from it to the door or window itself. When the door or window is opened, the magnet is pulled away from the transmitter, which will then send a signal to the alarm panel and activate the alarm.
Install the alarm siren in the same fashion as you did the control panel. It should be in a main area of the house so it can be heard everywhere if it goes off and it must be close enough to a power outlet so its power cable can reach. Drill a hole in the wall and a second one under the outlet and run the cable through. The siren must be programmed. This is normally done by entering a disarm code via a system of switches on the side or back of it with the help of a small screwdriver. Check the manual to verify the programming instructions.
Program the main control panel once everything else is set up. Follow the system instructions for this because the procedure varies depending on what brand of panel you are using. The disarm code you enter for the panel must be the same one that was plugged into the siren.
Activate the system through the control panel and test it for problems. Check the system and each individual sensor monthly to ensure your are properly protected without any system errors.