X1nject is just a program that injects the .dll file for the hack to work, because injectors aren't hacks, they just make the hacks work.
You have already done the first step (downloaded an injector). Second, go to the CrossFire hacks section and search for any undetected hacks. When you find one that suits you (OS, Country...) download the hack and put the .dll file somewhere on your computer. Third, open your X1nject and click "Browse". After that, search the files untill you find the place in which you have put that .dll file. After that, press "Auto inject" and finally start the game. Enjoy!
BTW, any MPGH moderator reading this post, please notify me if I could do anything to make my posts more understandable and simpler.