There are two ways of using PriceBlink for the iPad
From the PriceBlink App
if you open the app and shop through the built-in browser inside PriceBlink, it should show up automatically.
From inside Safari
If you're shopping inside Safari and want to check for lower prices, you can use thePriceBlink "Check Prices & Coupons" extension by clicking the Share button.
To use it for the first time, you'll need to activate it in your "Share" menu.
Activating PriceBlink in the Share Menu (One-Time Only)
Then just click on the "Check Prices & Coupons" button whenever you want to compare prices or find coupons.
You can see the instructions here