To configure auto pulling of documents, you need to generate the Client ID and Client Secret in SharePoint and register them. Follow these steps sequentially:

Generate Client ID and Client Secret

1. Open your site collection and click Home/ Documents.
2. Copy your SharePoint site collection URL (as underlined in the following image) and append "/_layouts/15/appregnew.aspx" to it, i.e.:
   https://ascertia0.sharepoint.com/sites/Integ-QA/_layouts/15/appregnew.aspx 
   
   
   
   
3. Browse the above URL (i.e. https://ascertia0.sharepoint.com/sites/Integ-QA/_layouts/15/appregnew.aspx) and fill-in the form as explained below.
   
   
   
   
4. To fill-in the forms:
   • Click the Generate buttons to create exclusive Client ID and Client Secret for your Auto-Pull configurations. 
   • Specify any Title for this configuration, i.e. SH-SharePoint. 
   • Now specify the App Domain and Redirect URI according to your deployment. If you dont have App Domain and Redirect URI, fill-in the fields with the exemplary values as quoted below these fields. Click Create.
   
   
   
   
5. Copy the Client ID and Client Secret values and click OK.
   
   
   

Register Client ID and Client Secret

1. Open your site collection and click Home/ Documents. 
2. Copy your SharePoint site collection URL (as underlined in the following image) and append "/_layouts/15/appinv.aspx" to it, i.e.:
   https://ascertia0.sharepoint.com/sites/Integ-QA/_layouts/15/appinv.aspx 
   
   
   
   
3. Browse the above URL (i.e. https://ascertia0.sharepoint.com/sites/Integ-QA/_layouts/15/appinv.aspx) and register the client ID and client secret as explained below.
   
   
   
   
4. Specify the client ID generated above in the App ID field and click Lookup. 
   
5. The data in the Title, App Domain, and Redirect URI fields will be auto filled-in as per the supplied values above.
6. Specify the following code in the App's Permission Request XML field. Click Create.
   
   
   <AppPermissionRequests AllowAppOnlyPolicy="true">

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

           </AppPermissionRequests>
   
   
   
   
7. Click Trust It.