@george.soong
By memory, not having TM at hand....
1) Click on PH 3/4 so that it becomes lighter color than other outputs.
2) Adjust faders of inputs and playbacks to volume/mix required.
3) Place channels to stereo image as needed using dials on inputs and playbacks. I am not sure if the pan dial is directly visible or one has click the "setup" icon of the fader...
I think, there is also srereo dial on outputs, but that is for further 'ballancing' stereo image, but main work has to be done on inputs and playbacks (if they are mono and not already stereo).
I recomend to go through all RME videos for TM several times. It did help me a lot. TM is great tool, but one has to invest time to understand the concepts. It works in some ways different way one would think without comprehending concepts behind.
I have been totally lost at first.