An instance is a logical entity that you use to manage backup and restore operations for all the databases that are created in that instance.
By default, the Commvault software automatically discovers and displays the instances that are available on the SQL Server.
From the navigation pane, go to Protect > Databases.
The Instances page appears.
Click Add Instance, and then select SQL server.
The Add SQL server instance dialog box appears.
From the Server name list, select the server that contains the SQL instance that you want to add.
From the SQL Server instance list, select the SQL instance.
To use a specific account when you perform backup and restore operations, select Impersonate user, and then in the User name and Password boxes, type the user credentials.
Verify that the account that you want to use can perform backup and restore operations. For information about the required permissions, see User Account Configuration for the SQL Server Solution.