I feel Twilight is being... overconfident...
These are some amazing models and I cannot wait to use them... But my immediate (and only) question is why is there only Photoshop files in the "Blender_Ponies" folder of the source files?
Sorry for the late response! To answer your question, it much depends on what your trying to download through. If through DeviantART, then there should be a button on the right of the submission with download inside... If your using the new "Eclipse" interface currently in testing, then there should be a down arrow-like icon next to the "Add a Group" button which will download it for you.
If all this sounds too complicated, then sign into Steam in your internet browser and click on the link in the description (the word "Workshop" that is underlined), and click on the "Subscribe" button on the page!
I hope this helps! ;)