Create a workflow with elevated permissions by using the SharePoint 2013 Workflow platform

To allow workflow to use app permissions

1. Click the Settings icon as shown in the figure.
   
   Figure: Opening the Site Settings page
   
   
2. Go to Site Settings.
3. In the Site Actions section, select Manage site features.
4. Locate the feature called Workflows can use app permissions, as shown in the figure, and then click Activate.
   

   Caution
   This feature will not activate unless you have properly configured the SharePoint 2013 Workflow platform and also apps for SharePoint.

   Figure: The site feature, 'Workflows can use app permissions'
   
   

Granting full control permission to a workflow

In order for the workflow to function properly it must be granted full control in the site. The following procedure grants the full control permission to the workflow.

Important
The procedure assumes the following: The procedure must be completed by a user that has Site Owner permissions. The workflow must already be published to the SharePoint Server 2013 site.

To grant full control permission to a workflow

1. Click the Settings icon as shown in the figure.
   
   Figure: Opening the Site Settings page
   
   
2. Go to Site Settings.
3. In the Users and Permissions section, select Site app permissions.
4. Copy the client section of the App Identifier. This is the identifier between the last "|" and the "@" sign, as shown in the figure.
   
   Figure: Selecting the App Identifier
   
   
5. Navigate to the Grant permission to an app page. This must be done by browsing to the appinv.aspx page of the site.
   Example: http://{hostname}/{catalog site}/_layouts/15/appinv.aspx.
   The following figure shows an example.
   
   Figure: The appinv.aspx page and URL example
   
   
6. Paste the client id in the App Id field and then click Lookup, as shown in the figure.
7. Paste the following Permissions Request XML to grant full control permission.
   
   Copy

   <AppPermissionRequests>
       <AppPermissionRequest Scope="http://sharepoint/content/sitecollection/web" Right="FullControl" />
   </AppPermissionRequests>
   
   

   Caution
   There are no placeholders in the Scope value above. It is a literal value. Enter it exactly as it appears here.

   The following figure shows an example of the completed page.
   
   Figure: Looking up an App Id
   
   
8. Click Create.
9. You will then be asked to trust the Workflow app, as shown in the figure. Click Trust It.
   
   Figure: Trust the Workflow app
   
   

Reference link:
https://msdn.microsoft.com/en-us/library/office/jj822159.aspx