The Edit | Replace menu option brings up the Replace dialog box.
Replace dialog box
This dialog box is an extension of the Edit | Find command. This allows you to search for a specific term and then replace it with the term entered in the Replace with box.
The Find Next button searches through the Basic Script Editor and brings up the first instance that meets the qualifications entered in the dialog box.
The Replace button allows you to replace what has been found (using the Find Next button) with what is in the Replace with box.
The Replace All button allows you to replace all instances in the Basic Script Editor that meet the search qualifications with what is in the Replace with box.
The Cancel button closes the Replace dialog box.