If you want to see or print an invoice from one of your previous booked appointments you have click on "Appointments" On the leftside menu of your personal dashboard.
Once you clicked on "Appointments" you can click the appointment you wish to see the invoice of. As a patient you can only see the invoices of appointments with the status "Ended".
After clicking on the appointment, click on "Invoice 00000" under "invoice" to see the invoice.
You can now see the invoice and are able to print it by clicking on the "Print" button located in the top right of your screen.
I hope this helped!