1. Inside Sales go to the Settings tab and then select the toggle, Enable Sales.  
2. Then, go to the Payments tab and choose one of the online payment gateways. 
3. After that, feel free to create a new Pricelist if you wish, or use the Pricelist already created with Bay Photo Labs. 
4. Once you have that set up, go to your gallery, select Sales from the client options and Enable Sales by then choosing a Pricelist to add to that gallery. It's that simple. You can preview your gallery and the shopping cart will be enabled. This will allow your clients to easily place an order.