Shopping cart a payment

Hi, I’m having trouble activating the shopping cart icons and completing the activation of the payment process.
When I click on the cart picture of the selected product, the action takes me to a page with just that product on and the opportunity to ‘leave a reply’. Clicking ‘next’ or ‘previous’. Just takes me into the next product.
I just need to know how to activate the order and payment process. Right to the end.
Many thank you’s,
Nicola

https://www.ads-software.com/plugins/sunshine-photo-cart/