For a shared channel, you can set the master as a regular master channel. The master is always transmitting, so after every transmitted message you will get an EVENT_TX to indicate that you can set the bytes for the next message that will be sent out. To send a message to a specific slave, you need to set the slave address in the first 2 bytes of the 8 byte data payload. For example, to send a message to a slave with address 1, the data payload would need to look like this:
[01][00][00][00][00][00][00][00]
… where the first two bytes are the address and the last 6 bytes are your data payload.
Slave Channel:
On the slave side, configure the channel as a “Shared Receive Channel”, or 0x20 for the Channel Type. You also need to set a slave address for your device using the message Device Serial Number (0x61). The slave message period must be the same as the master channel message period. However, the slave will only recieve messages that are addressed to it. The slave can send a message to the master iff it gets a message addressed to it from the master. So if you want a shared slave to send a message back to the master, you need the master to send a message addressed to the slave first. Also, the slave will only send a message if you command it to using a broadcast, acknowledged or burst message type.
I hope this clears things up somewhat. It is really easy to do all this using ANTware and a couple of dev kit modules.