The Intel® XML Software Suite preferences panel is opened from menu → → +XML+Intel® XML Software Suite
After installing the Intel® XML Software Suite you will have to browse its installation directory from the preferences panel in <oXygen/> and choose the intel-xss.jar jar file.
You will also need to update your PATH environment variable for Windows or the LD_LIBRARY_PATH environment variable for Linux/Mac to include the path to the system libraries(.dll/.so) distributed in the Intel® XML Software Suite. For details please consult the Intel® XML Software Suite manual.
After updating the environment variables you will need to restart <oXygen/> so that they take effect.
Depending on the version of Intel® XML Software Suite that you are installing, the environment variables may already be updated at installation time.