How can I modify the "Playlist" Storymap to include a basemap switching widget?

[BrettElliot]

I'm fairly new to HTML and Javascript.  I would like to modify the default "playlist" storymap template to include a basemap gallery widget.  Can someone help break down the steps to do this?

This is what the default template looks like:
http://storymaps.esri.com/stories/2013/20towns/

Here is an example of the modified playlist template with the basemap gallery widget.
http://fishandgame.idaho.gov/ifwis/maps/wma/

Thank you for your time!