how to implement app login in custom web app?

[GirishMeena1]

I created map, web mapping application on ArcGIS Online and wanted to access map using this app (but app hosted on my server using app login). We can create web application using many default template on ArcGIS Online. we can also download source code of these JavaScript applications and can host them on own servers.But I am not able to find any example which can guide me to modify app code to use app login.

I already know following steps:

• Register the app and get client id (app id)/client secret (app secret)
• Using POST request get access token from https://www.arcgis.com/sharing/rest/oauth2/token/
• What next? Not sure
• How to modify code in my downloaded app to access map.
• Downloaded app folder structure

Following are resources i refereed 

Implementing App Login | ArcGIS for Developers 

ArcGIS REST API 

Add items—ArcGIS Online Help | ArcGIS 

Thanks