PTStitcher is part of Panotools. I offered you a link to it in a previous post.
Panocube will want to know how to locate PTStitcher so you will need to install the folder on the "C" drive also then open a second window and then drop PTStitcher and drop it on top of Panocube Plus. (Just as you would a panorama image!) You only have to do the "path" showing of PTStitcher to Panocube Plus once.
Yes, seeing can make it all look much easier.
Hope it does help.