If you're performing bank reconciliation and notice that there is a statement entry on the left hand side that is not associated with any payment on the right hand side, you can create a new payment within the reconciliation screen.
Simply click 'New Payment' on the relevant statement entry.
You will then be able to choose the type of payment that this was and Crunch will generate the details to match what is on your statement entry. You can then click 'Create and match' to form this payment in the relevant section of the app, and reconcile it too.
You can then continue reconciling as you wish.