Welcome to the Reports forum!
If this is regarding someone cheating ingame please make sure to use /report before you create a thread as it sends us a replay of the reported player.
To create a report simply create a new topic with the following template:
Reported Player: Replace this with the username of the player you're reporting
Report Reason: Replace this with what you're reporting them for along with proof (if possible)
Used /report: If this is an ingame report, please let us know if you used /report