Ok....I borrowed a record player (the old fashioned all in one kind that has it's own speaker). When I plug into the headphone jack I only hear it playing in my left ear. I thought that was because these old ones only had mono sound so that's why I only heard it through the left side. But maybe that's not what mono sound does?
That's entirely possible, it's possible that the entire system is monophonic. But, wouldn't you rather get a true stereo turntable and get both channels off your stereo records? Or are you working with older, monophonic records too? (Definitely not an impossibility... I've done quite a number.) Personally, I'd look for a new turntable, with a built-in pre-amplifier that will give you a stereo input to your sound card, because "simulating" stereo isn't as good as the original.
So, if you're stuck with the mono setup, Sound Editor doesn't give you a good way to copy one channel to the other, so what you want to do, is hit up your local radio shack and get an adapter with a single, 1/4" mono plug at one end, and two RCA jacks at the other. Or some combination that will give you this. Now you can plug your stereo cable into the two RCA jacks and the 1/8" stereo plug into your sound card, and get the same signal into both channels. Once you've got your songs recorded, open them in Sound Editor and under Sound Effects (or Sound FX, I forget how it was labelled in EMC 7.5) look for the mono-stereo effect. You can listen to it as you play the songs to see what setting sounds best to you. Then when you're done, select "Export Current Clip" and select a folder to save it in, then click the "Export" button.
Hope that helps!