Re this post: Generating an email alert workflow not working
I created a Site Workflow, but I'm not sure how to create the Loop, or the condition "The contents of this loop will run repeatedly while 1 equals 1."
To use Loop in a workflow, you need to make sure your workflow is a SharePoint 2013 platform workflow. If SharePoint 2013 platform is missing, you need to install and configure Workflow Manager for your farm.
More information about installing and configuring Workflow Manager, you can refer to: Workflow Manager Configuration For SharePoint Server 2013