momentary switch latching circuit
simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. Redrawn circuit.


  I'm thinking V+ goes to the battery pack positive ...


Correct.


  ... and Vout to the negative, ...


No, VOUT is what drives the load. That's what's driving D1, the LED, in Figure 1.


  ... but I have no idea where the ground connection should go. 


In most circuits with a single supply voltage negative is the "ground" or 0 V or reference rail. I've shown it heavy in Figure 1 which makes it clear. 

CMOS inputs should not be left floating so NAND3 and NAND4 have their inputs grounded. They could be connected to V+ if it was easier.