This plugin works at the order level. So, you will find the Delivery Date Field on the Checkout page of your store. There are multiple options available under General Settings > Appearance section to change the placement of the Delivery Date Field on the checkout page - https://prnt.sc/10buh04 

Also, you can allow your customers for selecting delivery date on the Cart Page too by enabling the 'Delivery Date field on Cart page' option present at Order Delivery Date >> Settings >> General Settings >> Appearance tab.