Ok and format
Go to the link they gave you and when you open it you will see this: Show content
(https://iili.io/HDfOa2f.png)
go to Board Rules and Format than scroll down and you will find two formats: Show content
(https://iili.io/HDfOc74.png)
the first one is to report some one in-Game offence and the second one for Forum reports.
choose the one you going to do and go back to this link https://cit.gg/index.php?board=251.0 and make new topic and paste the format and fill it
Please, follow this requirement when you make complaints in the future:
Topic title must be: "Complaint - Offender's name - Reason".
Locking this topic as you've got your answer already.