Hi saurabh,
To grant login access there are two methods, depending on whether you are a System Administrator or any other type of user. Learn how below.
System Administrator
Depending on your Organization, the “Setup” button will be beside your name at the top right of the page or listed as a drop-down option when you click on your name.
1. Choose one of the following in Salesforce Classic User Interface:
-Click on Setup | My Personal Information | Grant Login Access.
– Click on Your Name | My Settings | Personal | Grant Account Login Access
2. Set the access expiration date for “Salesforce.com Support” (Minimum of 1 month for technical escalations).
3. Click Save.
Choose one of the following in Lightning Experience User Interface:
1. Click on your avatar in the top right-hand side of the screen and choose “Settings”.
2. Click on Grant Account Login Access.
3. Set the access expiration date for Salesforce.com Support (Minimum of 1 month for technical escalations).
4. Click Save.
All Other Users
1. Choose Your Name | My Settings | Personal | Grant Account Login Access.
2. Set the access expiration date for “salesforce.com support” (Minimum of 1 month for technical escalations).
3. Click Save.
Thanks.