This tab  is selected by default. Start your configuration here.
If Audio Level  indicators (blue) are both very low then it means that audio does not reach SmartPropoPlus.
There could be several reasons. Take a look at the list of Audio Input :
Have you connected the cable to the default input as indicated? If not, select the right one.
Here: socket Line in at rear panel (pink) in sound-card Realtek High Definition Audio
Are you sure the cable is good?
Does the transmitter function correctly?
Also, make sure that SmartPropoPlus reads the correct audio channel (Left/Right) and that it is set to 16 bit.
If SmartPropoPlus is now functional you can press button Minimize and start simulating.
If SmartPropoPlus is now functional but the computer is noisy then learn how to mute the transmitter.
If SmartPropoPlus is still nonfunctional try to configure its decoder - Select tab Transmitter.