You look at the back of the book--which most likely means the index--and you look up the subject of your question. You turn to the page indicated, you read the material and think how it applies to the question you have. (Key words: read and think.) Then if you still don't understand, you ask for help clarifying what you've read, and you say thank you. You say that first, by the way. Hope that answers your question.
Look at the back of the book. Maybe she wants you to try the index or glossary before you ask her. I'd guess she is wanting to build independence in you. It's so easy to ask for help, but in life you need to try to find the answer on your own. Also, in some books, the answers are in the back!