Kip . . . as was already mentioned by Jim, the pigtail people refer to under the seat is actually located at the base of the ROPS on the TC24D and your dealer already used it for the AUX light. That pigtail is NOT switched and is always hot. The AUX light should have its own switch on the top.
If you are looking to wire up some additonal lights, you will have to run new wires. The positive wire needs to go to a power source, the negative wire would be grounded on any part of the frame of the tractor. An easy place to draw power from on the TC24D is located on the left side of the engine at the alternator stub. It is easy to find. Simply lift the hood, then take the left exterior engine panel off. Walk up to the front of the tractor and you can easily trace the power wire from the batter back to a bolt on the left side of the engine. That is your alternator stub, and you can connect up to that point for an easy access to power. It is always hot, so you can use lights when the tractor is off. If you want to have your lights tied to the key, then you'll need to tap into your fuse box or into your light switch. As you said you never did much automotive wiring, you might want to go the easy route.