Alternate install method
I was also having this problem trying to install from the stock browser, getting the message"there is nothing that this file can be opened with .do you still want to download it?
So, I downloaded them to sd card to show as .apk, then installed(shows as .apk in es), i use miren to download them which sends to the sd card(under miren browser> download, then I use es file explorer to open them which brings up the package installer screen and just hitting install lets you install it.
Want to delete a skin? In the skin picker menu, select a skin like you want to apply it, hit menu, then delete.