Ask your gas and electricity supplier to mark the gas and electric lines. This will aid by avoiding the wires while digging. With the help of a post-hole digger, dig a trench from the lamppost to the power supply. Make sure that the power supply is near.
Next, lay the post on its side near the hole. From the hole at the bottom of the post, put in the wire and pull it till the top, some part should be over hanging. Make sure the wire is secure, so that it does not fall back inside the shaft. With the help of wire strippers, remove around 3/4 inch of insulation from the wire. Cover it with electric tape and cap with a connector. Then according to manufacturers instructions, push the wire connections into the pole.
Now mix the concrete and place it near the hole. With the assistance of your helper, lift and put the lamppost into the hole. A level can be used to ensure it is plumb. Fill hole with the concrete, while the other person holds the post. Put together the top of the lamp. Now test if the lamp lights up. Also check if the concrete has hardened, this would ensure stability.