There are two options for a Return that you will be able to use for your customer.
You will first want to create a Sales ticket like normal and add the product that you would like to return. Under the column Sales Type you will be able to choose:
Return to Stock : This option will be if you are having the customer Return the product and you would like to add it back to your On Hand amount in Inventory. You will need to make sure for this option that in order for the products to be added back into Inventory you will need to mark the Sale as Delivered.
The other option will be
Return and Discard: This option will be if you are having a customer Return the product and you are not wanting it to go back into Inventory because the product is no longer usable. So you would choose this option and Save and then the product would not be added back to your On Hand Amount.