How to install the Salesforce AppExchange app on Sandbox?

A lot of people facing issues to install an app on the sandbox.

Steps to follow:

1. First login to Production Org with your account (ie. not sandbox). — Check this first — You account is enabled with the “Download AppExchange packages” permission to install AppExchange apps.
2. Browse the AppExchange site to find the application you want to install.
3. Click Get It Now from the application information page. — If the listing does not have a Get It Now option, it may be a partner app that you can download and use outside of Salesforce. Contact the publisher for more information.
4. You will be asked if you want to install the app in Production or Sandbox
5. Choose sandbox and you will be automatically redirected to the test.salesforce.com
6. Enter in your salesforce sandbox credentials
7. Now just follow on-screen instructions.