Settings -> Customize Toolbars, then drag any files or folders you want toolbar buttons for to the toolbar.
See Editing the Toolbar for detailed information.
If you want Favorites directly on your toolbar, add a button which runs Favorites SHOWICONS NOOPENINTABS (or copy & paste the similar one that is already in the default Favorites menu) and it will turn into your favorites list when you click OK to exit Customize mode. The two extra arguments (SHOWICONS, NOOPENINTABS) are not required, but will probably be desired.