How does ZillaTube Work?

Okay, I had just downloaded ZillaTube(I clicked Free Download) and when I opened it, what popped up was an "Unregistered" pop-up window that looks like a sign-up pop-up. I am only able to click three buttons that might let me continue on that window: "Buy Now", "Unlock", and "Try It!". I don't know what to do next only because I haven't been given permission by my mom to use it as of yet, and I believe the button "Try It!" may let me continue free if I have a code to enter. Why is there have to be a code? Is it like making an account? I need some help.