Chapter 15 Unified Threat Management for FortiOS 5.0 : Application control : Enable application control : General configuration steps
  
General configuration steps
Follow the configuration procedures in the order given. Also, note that if you perform any additional actions between procedures, your configuration may have different results.
1. Create an application sensor.
2. Configure the sensor to include the signatures for the application traffic you want the FortiGate unit to detect. Configure each entry to allow or pass the traffic.
3. Enable application control in a security policy and select the application sensor.