How to set a radio channel?

Click on the lower-right selection box over the large dial knob. It's a single-slot constant combinator in disguise. Channels take the signal count into account, so IronPlate(2) is different to IronPlate(17).

How to connect to the circuit network?

Attach a circuit wire to the upper-left selection box (the I/O port), behind the aerial. It's a decider combinator in disguise. It's not operable, but accepts wires and can be used like a power pole to observe signals on the chosen radio channel.

How to pick-up/mine/deconstruct the radio?

The upper left selection box is not operable for technical reasons, so mining by hand or removing by robot both use the lower-right selection box. Removing the Radio will automatically clean up the I/O port too.

Why does it appear twice in blueprints?

Both the Radio and the I/O port are included in blueprints in order to preserve circuit connections. Only the Radio item is needed though, and placing it will automatically revive and connect the I/O ghost.