Contact your local gas and power companies and request they mark the area around your home where gas and power lines run. This will help you avoid hitting wires when digging the post hole. Locate the lamp post close to a power source.
Cut your concrete form to the specifications outlined in the manual for the desired lamp post. (You can shop for lamp posts at home-and-garden stores). Pull the power cable of your lamp post through the hole of your form and to the power connection you are using.
Dig a hole at least 18 inches deep and wide enough to fit your concrete form. Set the lamp post and concrete form into the hole. Dig a trench from your power cord to the power source. Pull the conduit through the trench and connect before covering it up. Connections of the lamp post will be laid out in your product manual.
Mix and pour concrete into the hole. Mix the concrete according to the manufacturer's directions on the bag that you choose. Pour concrete in the hole up to five inches from the top. Place the mounting bracket of your lamp post into the concrete and thread bolts into concrete. Let concrete dry.
Assemble the top of the lamp post if the post you purchased arrives in parts. Test the lights and make sure that the concrete has dried and that all parts of the lamp post are stable.