I had the same issue, but it ended up being really simple, at least for the international cutlass I was working on. Most passenger seats are manual. Start there and take that seat out first since you don't need a power source.
Once it is out, the passenger side will have an unused power connector exposed on the floor. Connect the orange wire to your dewalt battery, and the black wire to the opposite side of your battery. If you have alligator clips, they would probably work best.
Now that you connected power, go over to the driver side and use the buttons to move the seat forward/back.