First make sure there is audio at the headphone jack, using headphones. Then, assuming you use the proper TRS plug, as part of an adapter that splits the L and R signals each to its own female RCA, then each of those connects to a cable that goes to one of the two input channels of the Behringer, then turn up the contgrols on the Behringer to the right level, you should get audio.
I was trying to go from a male 3.5 mm to a male TRS Plug. I am assuming that won't work because it doesn't split the channels properly? I just ordered a male 3.5 mm that splits to 2 male TRS Plugs. Should that work?
I only have an option for XLR or TRS into my amplifier. I have the RCA's to 3.5mm, but there is nowhere to plug it in. The second suggestion that you gave is what I just purchased based on the suggestion. Thanks for the help. I hope that it works.