the previous answers transfer you to the log in page..... Anyways, here's the right answer:
1.Log in
2.Go to "Support"
3.Then, look at the right, you will find "Web Form". Click it
4.Pick the game (In your case it's crossfire.)
5.Then another box will appear under it. Pick the "Hacking Report" option.
6.Fill-in the required information then attach the replay file (Which you must save in order to be able to report the guy).
7.Click Submit.
That's how you report a hacker.