How do I reset my website?

I recently purchased the theme “Highend” from Mojo Marketplace, and, being the novice I am and not knowing that installing your own theme was possible, I bought professional installation for a hefty extra $50 or so. On Mojo Marketplace, making your website look like the demo does actually also costs extra money (around $50 as well). After becoming frustrated with my website (although I am new to this so that’s part of it) because my website was plain white and boring looking, and I couldn’t figure anything out, I did some research and found that self-installation and demo-installation were completely possible, and really rather easy. I looked in my sidebar to find the make-this-website-look-like-the-demo button, which I saw done on a video tutorial, but found the button to not be there. I did more research and found a button that could totally reset your website, so I could install the theme and demo on my own, and maybe the button would show up, but the button to reset the website isn’t there either!! I’m very frustrated and confused, PLEASE help me out!