You can print a receipt by navigating to the 'finance' area in a patient record.
Click 'View' beside the payment that you want to print a receipt for.
When you are in the payment there is a ... button then 'Print invoice' button at the top right hand corner which you can see in the image below.
When you click 'Print invoice' this opens up the receipt in print preview mode where you just need to click 'Print invoice'.