After installation, go to invoices and create multiple invocies for same customer.

Now, go to list view of invoices, here you can select number of invoices and click on action and select Register Payment

On clicking Register Payment, there is one wizard will open with poulated amount of all selected invoices.

Now, assume that if you pay less amount that total amount, then you will see two options to settle this difference amount.

After invoices payment, you can see created payment.

You can see invoice paid invoice. It will settle difference amount and close (paid) this invoices