Within each Group you have the ability to add notes to communicate important information like delivery days. You can customize this message for each Group. First go to your "Groups" tab, hover over the Group you want to add the information to, and then click on "Edit". Enter the notes in the "Notes to Show Resellers In Group" field, and click "Save group".
These notes will show on your beer's detail page - this way a Reseller will be aware of the information prior to purchasing the item.