To sign in to your Google Account (or any Google product): Go to the sign in page of the product (for Google Accounts it is myaccount.google.com). Enter your Gmail username (everything that appears before '@gmail.com'). Enter your password.

Another way to find Gmail email address from the desktop website or the official Gmail app is to select your profile image at the top right. If you're on a computer, this shows the email account you're using right now and any other Google accounts you're logged in to in the current browser session.

Most websites' or services' login pages can be accessed by clicking a Log In or Sign In link somewhere on the home page (usually in the upper-right corner). Then you'll enter your email address (or other types of username) in the "Email" text field and your password in the "Password" text field.