Hello Sir Mubasshir Pawle,

To change the Email content, you will need to locate Joomlafolder\language\ [the language you using ]
for example the below sentence is what you wanted to edit e.g.

COM_EASYSOCIAL_EMAILS_REGISTRATION_NEW_USER_REGISTERED="This is a notification to let you know that a new user has registered on the site. This e-mail contains their details"

which actually meant that this sentence are stored in COM_EASYSOCIAL_EMAILS_REGISTRATION_NEW_USER_REGISTERED

The email content will change but unfortunately I'm unsure where you want me to edit.
Do you mind providing a screenshot of what you wanted to change?
Your credentials of FTP, backend can be a helpful hand to us if you feel comfortable to share on Site Details:

Do correct me if you found me wrong and let me know more information about your changes?