The paddle cable is probably already attached to your iambic paddle. If it is a 1/4" style you will need a 1/4" to 1/8" adapter.
The keying jack on most radios is a 1/4" stereo phone type which accepts an iambic paddle input. Newer radios are now using an 1/8 inch key jack. K42's output jack is an 1/8" inch stereo receptacle. Disable the radio's internal keyer and connect key to tip and ground to sleeve. We recommended using a stereo connector leaving the ring unconnected.
The audio cable is dependent on the radio you are using. The best solution is to use the radio's line output which is usually on one one the accessory DIN connector. Refer to your radio manual for details.