Hello Brian,
In the into ui folder, there are a bunch of jpg's. and also a file called PluginGallery3.htm. These go into the folder called ui. The picture you show there is the plugin gallery. The sidepane instructions just add a "button" to the area where the history is located.

 

So to recap:

commands in the commands folder.

Contents of the "into ui folder" into ui folder

sidepane.htm into ui folder

plugin.png into icon folder

Let me know.