Is this the Charbroil 2-pc CI grate for the 22 kettle? If so, you'll need to get some solid type fat (Crisco, lard, etc.) to coat the grill for a
good coating.
Then just do a quick soap wash to clean, towel dry, fire up your kettle to 300-400 degrees, coat the grill grate generously, then place it on the kettle.
Let it season ("cook") for about an hour, slowly open the lid to check, restok with coals of necessary. It's gonna smoke like crazy. After the first hour slap another coat of solid fatty on it again. Let it go another 30 mins to an hour, and cool down. It should be good and seasoned, ready to use.
Only issue you'll ever have is if you get temps up too high, or if overscrub or use too abrasive an item to clean. You could scrub the seasoning off and have to re-do. Or, like I did in my Bubba keg a couple of weeks ago, make the mistake of letting the temp get up to 600-700 degrees sustained, and basically burning the seasoning away (but it did a HECK of a job cleaning the inside of the grill!)