Plug the 1/4-inch Y-cable into the female connector of the guitar cable. Do this before plugging the male adapter into the guitar.
Attach one 1/4-inch extension cable into the red Y-cable connectors. Attach the other extension cable into the white Y-cable connector. This makes it possible to attach an external device.
Plug one of the cables that extend from the Y-cable into the amplifier and the other into your sound card, recording unit, pedal effect or computer. If you plug both cables into your amplifier, make sure to connect the red one into the connector labeled "R" and the white one into the connector labeled "L."