Addressing DAC through SPI

So, I’m working on a project that involves an AD8804 (8-bit, 12-channel DAC). I’m working off of the Menta ECG project as a guide and template for using the DAC. But the problem I’ve encountered is I have no idea how to address all the different outputs. Also, it’s 8-bit vs 12-bit in the example. The different outputs have an address listed in the datasheet of 00002 and 00012, etc.

Any advice or pointers on how to form a proper SPI transmission for this?