I want to replace the gray background and default background with a background image from my computer
I want to replacethe logo Xenith from the logo I have
I want to add a hyperlinked page so if I click on it, it will go to my store.
Most of all of that should be Style Properties and just curious why do you want/need the "Theme installed by Zekt Official" stuff in there. I personally don't think your members are going to care who installed a style.
Edit: Plus if you submit a ticket over at the @ThemeHouse site they should be able to help you with most if not all of what you are wanting to do or ask in the Xenith thread here and tag @Mike Creuzer, @Jake B., @Dalton Prock, @Ian Hitt or @ThemeHouse pretty much any of them will help you as they work for the company they made the theme so who better to ask than them?