The trusted source for installing the MetaMask plugin is the MetaMask website, at https://metamask.io/. From there, you can get the link to the plugin page appropriate for your internet browser. Ensure that you do not install this plugin from any other non-trusted website.
Once you have installed the MetaMask plugin in your internet browser, you should be able to see an orange fox icon in your browser plugin bar. First, you need to set up your MetaMask instance to get it started. Let's learn how to set this up on your machine.
First, you should see a welcome screen:
This is then ...