Basically it's easy.
Using the tiny word "sie" in German can be pretty confusing in the very beginning. It has different meanings, but will be used in very similar contexts.
We can distinguish between the capitalized "Sie" and the small "sie". Let's look at both in turn.
When "sie" is not capitalized, it can only be the 3rd person singular feminine (she or her) or 3rd person plural (they or them). Or alternatively, it might be she or they, but in their accusative forms, which would be "her" or "them".
So the possible translations here are:
When you encounter a capitalized "Sie", things are a little bit easier.
The question here is why the "Sie" is capitalized:
If it's capitalized, but appears in the middle of a sentence where a different pronoun wouldn't be capitalized, then it's translated as the formal you.
If it's capitalized, because it appears at the beginning of a sentence, for example, then you're in the very unfortunate situation where it could mean any of the meanings discussed above, but it could also be the formal version of "you".