Ensure that the amplifier is plugged into a power source, then turn the power switch to the "Off" position.
Plug either end of the guitar cable into the jack marked "Input" on the amplifier. This jack is usually found on the front.
Plug the remaining end of the guitar cable into the jack on the body of the guitar. Most guitars feature a front-mounted jack.
Make sure the volume on the amplifier is turned all the way down to prevent any loud surprises, then turn the power switch to the "On" position.
Turn the volume on the amplifier up until you hear your guitar to make sure you have wired it correctly.