When do I use brackets? Is it supposed to be like me replacing "she" and "I" and "me" to make it fit my tense? Did I use them correctly below?
Brackets indicate that someone other than the character or author is speaking.
First of all, you can go for years, decades even, without using brackets. Back in the typewriter era, they were mainly used for specific types of math equations.
Whenever I have seen brackets used within a quote, they indicated that whatever is within them is something other than what the speaker actually said, but it clarifies what the speaker meant. If you were to go to the indicated page of Dracula , you'd see that the narrator, Mina Harker, didn't use "she" and "her" in the places indicated, and used "me" and "I" instead. These bracketed changes make the passage a third-person one, which is more convenient for the writer using the quote, but keeps things in context while acknowledging that changes from the original were made.
When brackets are used in text, outside of quotes, it's an indication that someone other than the author (usually an editor) is inserting a comment, and it's generally labeled as an editor's note.