Go to the Yahoo Sign up page - if someone is already signed in, click on the "sign out" link in the top left corner and start over (to avoid any issues).
For "@yahoo.co.uk", go here; "@yahoo.ca" (Canada), go here; "@yahoo.in" (India), go here - in all three cases, click "Sign Up" near the top right corner of the page.
Enter your first and last name, as you want them displayed to your people you email. Fill out the rest of the top section accurately, since some of it may be used as verification if you forget your password; changing language from English to Spanish will translate the sign up form.
Under Select ID and password, type the first part of your desired email address ("username", which comes before the "@") - only letters, numbers, underscores, and up to one period.
Select a domain from the dropdown: "yahoo.com", "ymail.com", or "rocketmail.com" - and you might see local variations depending on your country (or the link you clicked earlier).
Click the "Check" button to see if this email address is available: keep going until you find one.
The "Password Strength" meter helps you pick a hard-to-guess password - combine numbers, symbols, uppercase, and lowercase letters to guarantee that; retype it for confirmation.
Entering an alternate email address will make the password reset process much easier.
Pick two security questions and type their secret answers, also for password reset purposes.
Enter the code in the image to "prove" that you are human, and click on "Create My Account". Correct the form if needed; you now have a Yahoo Mail account: use it to login to Yahoo sites (like Yahoo News, Flickr), to comment on news articles, or to check your Yahoo emails.