1: Go to this Google Account Signup page. If you are already logged into a Gmail/Google account, log out of that first, or open an incognito window.
2: Click 'create account':
3: Click on “Use my current email address instead”:
4: Complete the form and click on “Next”:
5. Enter the verification code sent to your entered email:
6: Continue as prompted. Privacy and Terms may appear, just scroll to the bottom of the page and then click “I Agree”
This should complete the creation of a Google Account with an Existing Email Account.