well, in the end you will want the ability to archive all your custom skin-related files into the *.tar.gz format. So, if you do not have that ability then perhaps you will also want to check out something like:
http://www.ultimatezip.com/
now, at this point you will also have the ability to
un-archive the *.tar.gz format which is what you could do to, for example, the default skin file(after you make a copy of it). Change "default.vlt" to "default.tar.gz" and then untar it into some folder so you can look at the files.
You will want to look at the skin building manual page and bookmark or download it:
http://www.videolan.org/vlc/skins2-create.html
Basically you will want to make a folder and get your .png's in there.. also perhaps font(s) as well. And then the main skin file which is named "theme.xml"(which you might have decided to copy from the default skin to give you a good base file
).
keep us posted!