I have already went thorough that FAQ.  It does not correspond to the same options that I have on my DIR-615.  Here are the options that I have:
Enable QoS Engine :  [ √ ]
Automatic Uplink Speed :  [ √ ]
Measured Uplink Speed : 724 kbps 
Manual Uplink Speed : 
 Connection Type :  [ xDSL Or Other Frame Relay Network Cable  ]
Detected xDSL or Other Frame Relay Network : [ Yes ]
I have no place the enter any QoS rules. 
Therefore, I ask my original question:
How do I use the QoS engine in DIR-615 FW: 2.25?