(theme: deCente) uploading question macbook air mountain lion

hello!

new to wordpress. i’ve successfully uploaded and activated several themes to use for my site. however, i am only able to do this with themes that come in the format of a .zip file….it seems some do, some do not.

as is the case with the current theme i am interested in: deCente
https://themeshift.com/theme/decente/

i’ve tried googling & searching the forums here for advice…and i cannot find what i need. perhaps i do not know how to ask the question i am asking, of course.

so, how can i install/upload a theme that does not come in a .zip file? i am happy to provide lots of other info about how this particular theme is downloading to my computer, just ask!

im on a macbook air OS X mountain lion.

thanks =) jennifer