By this I am guessing the main chat in-game. Simply open paw menu
Click through tabs until you see chat
click chat
then type and have fun meeting people.

In the case you can read chat but cannot actually write, you may have been banned or there is a bug. In either case, go to the Official SH2 Help Discord server and talk to the ADMINS and Moderators. They can check for you.

Hope this helped

~Happy Hacking~