Hi David,
If you are still trying to figure out how to set your planetary gear set, this tutorial may help! It's a bit hard to see the last gear mechanism however.
Tutorial on how to mesh gears to create epicyclic gear mechnism in pro engineer creo - YouTube
I've just finished a university project that required a planetary gear set, and I found that as Roderick stated, its in the order of assembling gear mechanisms. I started with the planet gears as they were my drivers, and then attached each one to the sun gear as per normal gear assembly.
Then I connected one of the planet gears to a second pin mechanism along the same axis as the sun. For example, one connection was a pin connection between the sun and the sun shaft, another to the planetary carrier, it just depended on the setup. The ring gear was fixed at the start in the assembly, and I attached the sun gears along it's axis and in reference to it.
Hope it helps! Someone else might as well benefit from this extended suffering while figuring it out!