Different uses for に?
 

I understand that に signifies direction and location. However, there's one phrase that I don't really understand:

このサイトについて

Intended translation being:
"About this site."

Why is the に particle used in this situation?

I've memorized the phrase as I understand all of the words that make up the phrase. I've noticed the に particle used in this situation with other locations as well, for example: Googleについて.

Sometimes it helps to analyze the contexts in which a particular particle is used to ascertain its meaning, other times it's just better to memorize a phrase outright, such as について = "about"
If you ignore the English translation, in literal Japanese something somethingにつく means to attach to something or adhere to something, so strictly speaking the に used here is the　に equivalent to "to" though I don't recommend memorizing it that literally.

You are thinking of 「付く」 when one should be thinking of 「就く」.

つ・く【就く】 の意味とは - Yahoo!辞書

But for making sense of everything, it helps to consider that:
(Yahoo Dictionary)