Question about Common Application Essay Citation?

I'm doing my common application essay about a scientific study that had a big impact on me (the original topic was: Describe a character in fiction, a historical figure, or a creative work (as in art, music, science, etc.) that has had an influence on you, and explain that influence.). I did some research online to include in the essay and I'm pretty sure some of the information is going to need citations. Where should this citation go, should it be in MLA or APA style and should I include it in my total word count? I just can't find any info on the common site about this sort of thing so any help would be appreciated.