I believe you simply type them out as normal into the crossfire chat, What you can not do however is use them in clan names or in Crossfire Usernames. Some characters will not show up in chat and may become a simply broken square. However the majority do work, as people using other language dialects ect.. Often use these.
They should work in Crossfire chat by typing straight into it. As typically a lot of other language users will use these codes - Please follow the tutorial completely - If this does not work you may want to ask one of those users who do use these symbols. (In game)