How do I add a second (third...) computer to my 0patch account?

Once you have one computer successfully registered to your 0patch account and licensed with a valid subscription, you can use 0patch on additional computer(s) by doing the following:

1. Add licenses for additional computer(s) to your existing subscription; (see How can I adjust the number of licenses in my subscription? and How many licenses do I need for my computers?)
2. Install 0patch Agent on additional computer(s), and when asked to SIGN IN, provide email and password of your 0patch account.