1) Carefully examine Carousel.skp. You will need to print 6 Flag.stl (well, you do not really need the flags, but the wife wanted them, so if you do too, then print one for each horse and one for the top of Canopy.stl), 5 Horse.stl, 1 Base.stl, 1 Bottom.stl, 1 Top.stl and 1 Canopy.stl. Print your parts in the color(s) of your choice then assemble following the Carousel.skp diagram.
2) Buy this motor: 6VDC 45 RPM Pinky Finger Sized Gear Motor 1" Long x 15/32" x 3/8" from either amazon.com or directly from http://sciplus.com/p/MICROMOTOR_47952 (this is the same motor I used in the Marbelvator design). In this application, I run the motor at 1.5 VDC and as such the motor requires 10 to 20 ma to run which is suitable for a small power supply, battery and/or solar panel use. Solder the obligatory red and black wires (about 4 inches each) to the motor plus and minus terminals respectively. Slide the motor into Base.stl, wires first, such that the motor wire terminals are parallel with the large rectangle at the bottom of Base.stl. Route the wires through the wire trough on the bottom of Base.stl. If you cannot find a 1.5 VDC power supply, use a 3 VDC power supply and use two 1N4007 diodes (or equivalent) to reduce the voltage.
3) I found if you print using Makerware, you will need to trim the flag staff and horse insert with a modeling knife.
4) It is helpful to test fit the motor output shaft on Top.stl before assembly. Make sure the motor shaft flat aligns with the flat in the hole in Top.stl before insertion.
5) If you have questions, place a comment and I'll try my best to answer them.