How to claim it? Quite simple.
Skip to step 3 if you already register but not yet use.
Download Uber app here.
Very simple requirement
(credit card NOT required)
After registered and "Sign In".... you are ready to request a car but wait....enter the promo code first.
Look for Menu (as per the arrow shown)
Look for "Promotions", the click "Add Code"
Enter the Promo Code MariUber and "APPLY".
Then you are good to go.