To configure an list or library for anonymous access steps are
Navigate to a list or library that the app for SharePoint that you
are testing accesses and open the List Settings or Library Settings.
For a SharePoint Online site, you must be logged in as a tenant
Choose Permissions for this list/library.
On the page that opens, choose Stop Inheriting Permissions on the
Permissions tab, and then choose OK on the confirmation prompt.
Choose Anonymous Access on the Permission tab.
On the Anonymous Access form that opens, select all of the
permissions that that users of the app for SharePoint require. You
can grant permission to View, Edit, Add, and Delete items. You
cannot grant Full Control, so anonymous users cannot change the
schema of the list or change list settings.