How to use the transaction BNK_APP

Dear SAP TR Experts,

May I know how to use transaction BNK_APP? This is to approve payment, does it mean when we use the F110 to generate payment proposal, we can use BNK_APP to approve the proposal so that to do to payment?

This is a stupid question, just want to know where is the source to-be-approved payment come from for BNK_APP?