You can update your delivery details in the app 2 different ways.
Option 1- Use the calendar strip at the top of the screen to select a delivery date. Then click on 'Manage Week' then choose 'Delivery Details'
The option to then edit your delivery address, day and time will appear along with the option to add/edit any delivery instructions. NOTE - Any changes made here are ongoing on the subscription and will need to be changed back for future deliveries if the change is only a one off.
Option 2- Another way to edit the delivery details is to simply click on the 'Account' tab at the bottom of your screen and then click on 'Account Details' and then you can select 'Edit' from there. It is also on this page that you can edit your preferred payment method.