For my essay, I decided that I want to use the phrase "Nolite Te Bastardes Carborundorum." Do I enclosed it in quotation marks or just title it as Nolite Te Bastardes Carborundorum?

Direct quotation
The kind of marks you use to identify this phrase will depend on its context in your essay. If you are providing it as a direct quote from the text, you should enclose it in quotation marks and provide a citation. For example:

The first-person narrator describes kneeling to find “[n]olite te bastardes carborundorum” scratched “where the darkest shadow fell” (p 66).

Note that, because the phrase is capitalized in the book but we need it lowercase in the quote, I have amended it using square brackets. This is to make the quote flow as part of the sentence. I have maintained the italics per the original text; this phrase is set in italics because it is in a foreign language (in this case Latin).
Description of the phrase
If, however, you were commenting on the historical significance of the phrase, not using it as a direct quote, you could do so like this:

The faux Latin phrase nolite te bastardes carborundorum appears in this novel and is taken to mean . . .

Note that I have italicized it in this sentence as well. Consistency is very important, and italicizing foreign words is a common practice across style guides.
As the title of your essay
If you were using the phrase as a title for your essay, not in the body, you could make a number of stylistic choices. If the whole title of the essay is simply the Latin phrase, you could present it in italics as follows:

Nolite te bastardes carborundorum

In AP writing style, only the first word of the title is capitalized. If your school or teacher uses a different style, you might need to capitalize all of the words. Check with the teacher who will grade your paper if you’re unsure about which words in a title should be capitalized.
If you were presenting it as a title with other text you could do so as follows:

Nolite te bastardes carborundorum: don’t let the bastards grind you down