Question

What punctuation mark is often used to insert exclamation text into a quotation

Answer 1

The answer is an exclamation point (!)

Answer 2

Assuming you meant explanatory text and not exclamation text, the answer would be brackets. For example, say your quotation is "She wrote the book." If you are quoting this directly in a paper, you want your audience to know who "she" is. So, you use brackets, and write the following: "[J.K. Rowling] wrote the book." Hope this helps.