really, it's pretty simple.  to use the character you bought...
on a pc:

• Open the zip file
• Drag the "Runtime" folder to the folder holding the runtime with v4.
• When you get a message asking you if you want to overwrite, say yes.  Windows will merge your old and new Runtimes.
• Start Poser.
• Load V4.
• Go to the Pose folder and look for the "VS-V4-CharacterCreation" folder.
• Apply the settings you want.

on a mac, it's harder because you don't have a copy/merge function.  you can handle that by going into the runtime folders and copying the appropriate folders.

the other content is a bonus.  it's not a waste of $11, because most characters cost at least that much.  if you don't use the merchant resources to make your own textures, fine.  no one's going to force you to use all of a product.  you can just use it like a regular character set.  but if you ever decide to add to that texture to make your own character, you'll find those psd files useful.