Also, just as a word of warning coming from experience.
You mentioned that you have an OPS head. If it's a chinese clone OPS head, take special caution regarding MOST (fibre optic) programming. The chinese clone makers like to say that MOST functionality works perfectly and is stable, but I've found on several occasions that's not true, usually due to substandard electronics on the on fibre optic transceiver built into the unit.
Unfortunately, Progman/SSS's error recovery for failed flashes or recovery for a communications interuption between the software and the head isn't all that great usually resulting in an unresponsive module. ISTA/P's error recovery is much more advanced and recovers from 99.99% of all failures without bricking a module.
To your question about where to connect the power supply, connect it to the terminals under the hood, just like you would if jumpstarting the vehicle.