I don't know anything about creating a 3D model. Is there somewhere I can just download a model to print, that someone else created?
YouMagine is geared more toward the capabilities of the Ultimaker2. Thingiverse is geared more toward the Makerbot printer, but many models will work on the Ultimaker2. Keep in mind, however, that not all models that are on these sites have been tested. Some might work and some might not. Check the comments box on the website for that model to see if others have actually printed the model in question. Have a proper look at the model in Cura to see if it looks like a printable object.