How do you connect to radios so we can talk to each other they are GMRS602CH audiovox radios

I assume you mean Synchronise audiovox. By that, I assume you have two of more radios that don't talk to each other. If you can provide a model number, I can guide you to a manual website.

the Audiovox AN400 is a television antenna for cars. If your radio has a TV receiver built in, it should be simple, or an adapter or two. If your radio does not have TV, there is no reason to hook this antenna to your radio.

Yes - the radio has cd changer controllers.
The Changer is FM modulated - and the radio becomes the controller.

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turn them on ... choose a channel to talk on ... press the press to talk button.

Need more information.
Do you know if either one:
1) turns on
2) receives (anything)
3) transmits
The site won't send a clarification request so I had to send it as a solution.

http://www.buytwowayradios.com/Products/Audiovox/manuals/GMRS-122-2CHom.pdf
click the link directly.

Two known causes of squealing when the radio is put under a load (such as when the PTT is pressed) are a low or bad battery, or being too close to another radio.

http://www.shopzilla.com/audiovox-gmrs70012-gmrs-frs-gmrs-two-way/11693654/compare

If your radios are set identical to one another, you simple need to press the push-to-talk button (PTT) and hold it in while talking. Let go when you are not talking, in order for the other person to be able to press their PTT and talk back to you. The monitor button is only for checking to see if other users are talking on your same frequency, and if so, you are to be polite and not talk over the top of them. (So the rules say.)

CHANNEL FREQUENCY 01 462.5625 02 462.5875 03 462.6125 04 462.6375 05 462.6625 06 462.6875 07 462.7125 08 467.5625 09 467.5875 10 467.6125 11 467.6375 12 467.6625 13 467.6875 14 467.7125