To cancel an order go to My Orders section. Once you are in the My Orders section, you have the option to cancel individual products in your order. However if an order has already been picked up by the delivery executive, you will not be able to cancel the order.
If the order status is 'Out For Delivery' then you can reject the order when the delivery partner calls you or when he visits your place to attempt the delivery.
In case if you have any issues in regards to the cancellation, please feel free to chat with the support team or mail us on firstname.lastname@example.org