Within the left side bar under EVENTS, select Events. This will take you here:
Select the desired event. This will take you here:
Within the horizontal navigation bar, select Order List. This will take you here:
Select your desired order. This will take you here:
In the top right hand of the pop up, select the green edit button. This will take you here:
Within the Guests/Non-Members Payments box, select the green box titled +Payment. A pop up will appear that looks like this:
Type in the required payment information.
Then, select the invoice in which you wish to apply a payment. To the right of the invoice under Amount To Pay, type in the amount that you wish to pay.
Once you have typed in your desired information, a green button will appear at the bottom of the pop up titled Submit Payment. It will look like this:
The payment will then be applied to the invoice.
These are samples.