Your customer will log into your Customer Portal using the email address on their customer account and the password that they have set up. If a password has not yet been created, or if they are unable to remember the password, you can Reset the Password to the Customer Portal.
Once they are logged into the Customer Portal there is an option for All Invoices on the left-hand menu. Clicking this will give them access to view any invoices generated on their account and a Pay Balance Due option will be available on the invoices with an open balance both in the table of invoices and also at the top of the screen.
After the customer clicks the pay option, they will be brought to a window where they can enter their payment details.
Payments made through the Customer Portal will show up in your account immediately and be available both in the invoice to which the payment was made and also in your Payments report in your Accounting header labeled as an Online Payment in the Received By field.