There are two main ways of paying a bill:
When you receive a printed or electronic bill from any biller.
To manually enter bill details from a (non-Bluechain) biller into the Bluechain app, see Enter and pay any bill.
In each case, you select a method of payment (eCard) and authorise the payment. The transaction is placed in the banking system, and when approved by your bank or card issuer, a confirmation is displayed in the app. Bluechain then uses the funds to settle the bill with the biller. In this way, you can pay any bill with a credit card (and earn rewards), even when the biller doesn't accept payment with your preferred credit card.