Plug the guitar cord into the "audio-out" port on your instrument. Most ports and guitar cables use 1/4-inch stereo plugs on each end of the cord.
Plug the other end of the guitar cable into the "audio-in" port on a UHF wireless transmitter. UHF, which stands for Ultra High Frequency, works best in indoor locations.
Use a stereo coupler matching the size of the guitar cable if the wireless transmitter has a stereo cord attached. A 1/4-inch coupler has a tube-like shape with jacks on either end and will work with most systems.
Power on the wireless receiver. Make sure the receiver uses ultra-high frequencies and is set to the same channel as the wireless transmitter.
Use the second stereo cable to plug the transmitter into the guitar amplifier. Plug one end into the "audio-out" port on the wireless receiver and the other end into the "audio-in" jack on the amplifier. Test transfer or sound by powering on all devices and strumming the guitar.