The first part of the video is for those just joining SL... then they talk about upgrading a classic system bod to Senra (nee NUX?).
One curious thing, the customization process does not explicity ask about gender/sex preferenece. Rather, it simply uses body shape and boyish/girlish naming.
Is this a hit or miss?
Oh... if you go to the Library folder in your Inventory (I am using Firestorm), you will find a new subfolder named Senra, which has subfolders for Blake and Jamie.
I realize it's too late for this venture, but just in case it helps anybody else: It may not be obvious you can edit stuff by right-clicking it in Inventory or the Appearance floater, so here's one way to do it:
That's supposed to show selecting the "Now wearing..." menu item from the "Avatar" menu. (That's obviously Firestorm. In modern viewers the Avatar menu is much shorter, with a separate "Me" menu for stuff that's not actually about the avatar.) Anyway, that should produce an App