From a console window, use the locate command to find mysqld. locate mysqld. If it was installed when you installed RH, it should show where it's installed.
If you installed mysql after installing RH, run updatedb first to update the database of installed files, then run locate mysqld.
If you run 'locate mysql' it'll show you everything with mysql (lowercase) in the name, including documentation. 'locate MySQL' (upper and lower case) will probably show you directories pertaining to mysql.