Searching starts from the top of the document. Type in your search term and press the Find button; Mosaic will jump to the first occurrence of the search term and highlight the matched text. Press Find again repeatedly to jump to subsequent occurrences of the search term. When there are no more matches, a dialog box will be popped up telling you so. (Pressing Return in the text field is equivalent to pressing the Find button.)
To reset the search process (i.e., clear out the search text and reset the search to the top of the document), press the Reset button at any time.
Every time you view a new document (by jumping to it via a hyperlink, or moving through the window history list, etc.), the search position will be reset to the top of the document as if Reset had been pushed -- but the search text itself will not be cleared out, for your convenience.
The two toggle buttons in the search window work as follows: