To find text within a particular script, click CTRL-F, or choose Find from the Edit menu. Once a word is highlighted, pressing F3 or SHIFT-F3 will find the next or previous occurence in the file.
Press CTRL-H or choose Replace from the Edit menu.
Press CTRL-SHIFT-F, or choose Find in files from the Edit menu. The results are displayed at the bottom of the editor, and you can click on them to take you to that line of code.