If you haven't used 3dmark.com before, you must create an account. The easiest way to do this is to run 3DMark or PCMark and after the tests are complete, click the VIEW RESULT ONLINE button. On the result page, you can create a new account either by entering your email address and a password or by signing in through Google or Steam. Alternatively, you can register a new 3dmark.com account.
When logging in later, please remember that the email address and password are case-sensitive, so type them exactly the same way as you did when registering. If you're still unable to log in, make sure that your browser has cookies enabled, clear all browser caches, and delete old cookies from 3dmark.com from your browser.