You can print these simple toys using the .stl files or modify the design using Autodesk 123D design.
These files come from my book, A Beginner's Guide to 3D Printing: 14 Simple Toy Designs to Get You Started (Chicago Review Press). How does a person with little or no computer design experience create an object to print? I think hands-on experience (an apprentice method) works well. The book goes through each toy, step-by-step with screen captured photos (using Autodesk 123D) for assistance. Word descriptions of the same projects using Sketchup are also included.
The book is available worldwide, wherever fine books are sold.
Generally, print at the lowest resolution with supports.