(Apologies for starting a thread for such a basic question, but I haven't been able to get an answer any other way)

Does anyone know how to shop through the Barclays Rewards Boost shopping portal?

When I go to https://www.barclaycardrewardsboost.com/, select a store, and click on "shop now", it asks me to log into my Barclays account. After logging in, I am taken to my account summary page, instead of being linked to the merchant's website.
I've tried to find a link to the portal within my Barclays account, but haven't been successful. As a result, I have been forgoing the extra points that I could have been earning with my Barclays Lufthansa Miles & More credit card.

Thanks