The Text to Find input box is where you enter the search string.

To begin the search, choose OK; choose Cancel to forget it.

If you want to enter a string that you've searched for previously, press the Down arrow key to show the history list, then choose from that list.

You can also pick up the word that your cursor is currently on in the Edit window and use it as the search string; simply invoke Find from the Search menu.

To take additional characters from the text in the Edit window, press the Right arrow key.