I am presuming you have a front loader. What I do is bolt an extension pole to my loader so that I can get some extra height, lets say 16' overall at the end of the pole with the bucket raised to the max height. Then I assemble the light (lantern, bulbs, cord, finiale).
Next, I add weights to the base of the light pole so that when its picked up at the 15' mark, the pole would hang almost vertical from this new c. of. g. Leave the extra foot to reach over the baseplate bolts.
When you raise the loader with a strap at the new c. of. g. (light + pole + added weight(s)), the assembly should want to travel with the base end on the ground at all times. lift it up and you can place the base on its foundation. You ought to be able to do this just by yourself since the tractor carries 99.99% of the weight. Bolt it up and remove the added weight(s). Strapped on suitcase weights work for me.
Having a smooth loader valve controller makes this easy because you can raise or drop the load very slowly. If you are going to have to travel some distance to the pole's new location use a rope to hold onto one end. They tend to want to swing around as you move.