INGAME USAGE
The CiA server will give you two radios, since ACRE currently does not support dual watch radios (alternate channels). One of these Radios is the AN/PRC-343 PRR (known as H4855 in Brtitain) which is the short range/squad radio. It should usually be mapped to the ALT Radio 1 key.
Local talking is, as usual, done via the TeamSpeak PTT key. You can press the volume key (CTRL-SHIFT-TAB if you did map it to the same key as me) and roll the mouse wheel to increase the range (up to some 150 meters).
The second one depends on the circumstances. For non-team leaders, you get an extra AN/PRC-152. The extra radio should be bound to ALT Radio 2, and is set to channel 16 (the command channel). Normally, you don't transmit on that channel as a grunt.
The team leader will get a long range radio based on "circumstances". If there is no backpack, the server will add one with a AN/PRC-177F. If there is a backpack, the server will add the same radio if and only if it fits in the backpack. If it doesn't then the leader will also get an AN/PRC-152 since that one has a pretty decent range.
In both cases, at the very beginning of a mission (or after a team switch to a hitherto unused AI) there will be a delay of a few seconds (where usually TFAR would say something like "getting radio ID from server") until radios are set up correctly (there is a hint in the corner that will disappear once the init is done). In that phase, you WILL have radios but the channels are not set up, so avoid doing radio checks until the hint has disappeared.
The self-interaction menu should list a "Radios" sub-item, where you can set some stuff like earpiece etc. By default, the long range radio is set to be right ear only. The menu can also be used to open the GUI of the radios.
The AN/PRC-343 looks like this:
Right clicking one of the knobs (volume or channel) will decrease, left clicking will increase the setting. Usually, though, you should not need to do anything (unless you switch to a different squad).
The handle on the side can be detached to change the channel block, however, it is more than unlikely that you will ever use this.