Unclear to Newbies

I downloaded this app and opened it before I even opened uber but never found any obvious way to sign up with it. Somehow I ended up signing up via the uber app and so miss my chance at $30 credit even though I havent even used this service. I found this app to be confusing for a newbie like me. Other newbies beware not to make the same mistake that I made.

NewtoUber about GO: Discount for new UBER® riders