shashi,
Thank you for your question regarding notifications of activity on your site. Although you didn't mention, I searched for the terms and it seems you are using Moodle.
I recommend following the guide James wrote on Configuring notification methods for Moodle.
Also, here is a helpful link to Moodle's official documentation on Available Update Notification.
If you have any further questions, feel free to post them below.
Thank you,
-John-Paul