"She wears yellow shoes."
Kimasu is for getting dressed in general, or for putting on things like shirts and jackets on the upper half of your body. Hakimasu is for wearing pants, skirts, shoes, socks, etc. on your lower body. There's also "kaburimasu" for hats, "kakemasu" for glasses, and other verbs.
It is the marker for the direct object. Direct objects are the complements to transitive verbs. Transitive verbs are the verbs that kind of -ask- for a complement, they don't have a complete meaning by themselves, or the meaning can be dubious.
In this example, the verb is to wear. I wear. But.. what do you wear? You wear -something-. This something is a direct object, and you'll use を after it, and only after it.
I put the websites instead of my bad explaination.
It's one of 助詞(じょし). You can search more good sites by use these words '助詞' and 'を'.
go for it! :D