How can I enable app step in SharePoint 2013 workflow and use the same to set elevated permissions for my list items?
Make sure that
- You have saved and publish your workflow.
- You are using site owner.
- the "Workflow can use app permissions" feature is activated by going to Site Settings > Manage site features.
If the issue still so you should
Grant full control permission to a workflow as mentioned at The Workflow was Suspended with Unauthorized HTTP / Elevate Workflow permissions in SharePoint 2013