How to Grant Login Access to support Agent in salesforce

steps:
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
- Non-Enhanced Setup Menu - Setup | My Personal Information | Grant Login Access.
- Enhanced Setup Menu - Your Name | My Settings | Personal | Grant Account Login Access.
The page will be as below

2. Set the access expiration date for support .
3. Click Save.

All Other Users:
1. Choose Your Name | My Settings | Personal | Grant Account Login Access.
2. Set the access expiration date for  support .
The page will be as below

3. Click Save.
Enjoy..