
You could refer to the following links to set SharePoint 2013 to allow anonymous access.
https://www.sharepointdiary.com/2014/05/how-to-enable-anonymous-access-in-sharepoint-2013.html
http://support.sherweb.com/Faqs/Show/how-to-enable-anonymous-access-to-a-sharepoint-site-sharepoint-2013