One of the most useful things you can do on your NOOK Tablet is search for a word or phrase in it. Try that with a printed book! You have two convenient ways to do it—the Reading Tools menu or the Text Selection toolbar.
To search using the Reading Tools menu, bring up the menu by tapping anywhere in the center of the screen; then tap Find. A search box and the keyboard appear. Type your search word or term, and then tap the Search button.
Tip
When the search box appears, you see two X’s at its right—one inside the box, and one to the far right outside the box. Tap the X inside the box to delete the search term already in the box. Tap the X outside the box to make the search box and keyboard disappear.
After a little while, a screen pops up showing you the results. You’ll see the chapter and page number, the text surrounding your search term, and the search term itself. Scroll through the results and tap any of them; you jump to that spot in the book with the search term highlighted.
Underneath the results screen, you see a Search toolbar.
You can type a new search in its search box, or tap the double forward
arrow to jump to the next search result, or tap the double back arrow
to jump to the previous search result. Tap the small Table of Contents
icon 
to the left of the search box to make the
search results screen disappear or to make it appear again if you’ve
made it go away.
When you select text and choose Find from the Text Selection toolbar, that does the exact same thing as choosing Find from the Reading Tools menu. The NOOK searches the book for the term you highlighted, and it shows the results in the same way.