How do I correctly wire an auxiliary battery 99 Suburban using existing GM equip??

[DeadheadNM]

I've got the 99 Suburban and an extra battery. The Sub came with an aux (LH) battery tray and I see attached to the under hood fuse block there are two battery terminals labeled "Aux A" and "Aux B". How do I wire up the aux battery without ruining the wiring?

My hope is that by doing so I have one battery dedicated to starting the Sub while the other can run equipment when the engine is off and drain with no consequence for starting. I've installed OEM aux battery setups in my 1972 Blazer and K20 - just not at all familiar with newer model trucks and couldn't find a related thread. Thanks, Pete