To manually process a payment you have one or two options.
Firstly, you will see the 'Collect Now' feature against each available invoice. On hitting this the payment will be sent to GoCardless to be created and will be deducted from the customers bank in 4 working days, this feature must be used before 4pm to kick start the process that day. If you hit Collect Now after 4pm GoCardless will still be sent the payment however they will not create the payment until the following working day.
Secondly, as a user on the account you can also process payments in bulk. Simply place a tick in the box along the left hand side, (there is a feature at the top of the page to select ALL available invoices).
You then go to 'Bulk Action' in the top right hand corner and select if you want to the payments processing there and then, this works the same way as using 'Collect Now' or, select 'Collect on Due Date' and all invoices will be deducted from the customers bank account on the Due Date only.
Tip: You can search for an individual invoice using the search bar on the top left hand side of the page.