Install Salesforce CLI

Step 1 : 
To download salesforce CLI, you can use following link:
a) https://developer.salesforce.com/tools/sfdxcli

 OR

Operating System	Link to Installer
macOS	https://sfdc.co/sfdx_cli_osx
Windows 32-bit	https://sfdc.co/sfdx_cli_win
Windows 64-bit	https://sfdc.co/sfdx_cli_win64
Debian/Ubuntu 64	https://sfdc.co/sfdx_cli_linux Download the archive from one of the URLs in the manifest, extract the archive, then run the ./install script.
Debian/Ubuntu x86	https://sfdc.co/sfdx_cli_linux_x86 Download the archive from one of the URLs in the manifest, extract the archive, then run the ./install script.

Step 2:

Step 3 :

Once installation is done, click on close button and open command prompt.

Step 4:
In command prompt,
a) We can check whether sfdx plugins are installed or not using following commands:
    sfdx plugins
b)  If you get error message like no plugins installed then use this command:
     sfdx plugins:install salesforcedx@pre-release
c) Verify again using command
     sfdx plugins