What version of Premiere Elements and on what computer operating system is it running?
You can apply Balance to favor more to one channel than the other, you can swap channels, use Left Fill or Right Fill, but you cannot separate channels in Premiere Elements. You can in the free audio editor named Audacity.
The available Premiere Elements audio effects are described in the Adobe Effects Reference document. In that document, click Show All and scroll down to the audio section of the document.
Please review and consider and then supply more information.
Any questions are need clarification on the above, please do not hesitate to ask.