This tab  enables you to select the correct audio to digital decoder that suits your transmitter.
The Signal Decoder  is set to auto by default. If it fails to select the correct decoder you might try to select a decoder manually.
In some cases of PPM signal, more than one decoder will prove to suit your transmitter. Experiment with all to find out which decoder suits your transmitter best.
The Green bars / should respond to your stick and the number of R/C Channels / should be correct.
If SmartPropoPlus is now functional you can press button Minimize and start simulating.
If the Green bars do not respond to your sticks then your signal might be corrupted due to a bad cable or a low quality sound card. You might try to check the audio level.
In most case you don’t need to use a filter. So if a filter is selected you should probably turn it off.
If the Green bars move correctly but the Red bars do not, try to configure its vJoy interface - Select tab Joystick.