I guess I'm missing something totally obvious here, and you all free to LOL forever

but I just have to ask.
I've looked at the small tutorial on the sigil-page, and in the manual, but I only see people opening f.x. the index.html file.
I have a folder with a html-book (java-programming tutorial in danish from this web-page
www.javabog.dk ), there's an index.html file, I can open that. As far as I understood to add the rest (which seems to be a mix of png's and jsp-files) I should right-click in the browser area and choose "add existing item...".
When I do that, the jsp seems to add itself in a folder called misc. However, double-clicking it doesn't make it show, as if there was no content.
I have attached the book which should be like this webpage:
http://javabog.dk/index_OOP3.html . I've added it here, but the zip-file can also be downloaded from here:
http://javabog.dk/OOP3/kode.zip
Any help on how to make an epub out of that html with Sigil, will be greatly appreciated.