I can bring each video with audio down to a timeline individually, but if I try to add a second, it will only allow it to be added to a different timeline, not the same one,which layered the audio instead of just linking them together when I rendered it. I thought this would be super easy, kdenlive seems pretty user friendly, but I'm totally stopped here on something that seems very basic. Im guessing it has to do with the fact that the audio clip that shows up with each is longer than the video for each...though there are no sync problems...but all my googling and searching here hasn't found a similar question yet. Am I missing something simple, or is it more complicated than it seems? If so, what do I do?

Firstly, it would help if you said which version of kdenlive you are using and on what OS. Secondly, a screenshot of your timeline or even a short recording of what you are trying to do is extremely helpful in troubleshooting.

Check the kdenlive manual for cutting and editing and the section about the timeline.

Whenever you try to insert a clip into the timeline where there are clips already make sure you have an audio track available (you can add audio tracks independently and kdenlive associates them with the respective and corresponding video track automagically) and that there is enough space for the clip to fit into. There are also different timeline editing modes available (normal, overwrite, insert) that change the way clips can be dropped into the timeline.

So much for the basics

the audio clip that shows up with each is longer than the video for each

This got me confused because when a clip in the bin has video and audio kdenlive splits the streams and assigns them to the corresponding track. By definition, the audio stream of a clip cannot be longer or shorter than the video stream and the two clips show the same length in the timeline. If there is no sound or it stops mid-way, of course, the audio track would not show any waves for that part and one could think the audio track is shorter. But that is not the case.

In conclusion, please check the above mentioned cases (is there an audio track for the video track you want the clip to be put in, and is there enough space - you may need to change the zoom factor) and that should solve the issue(s).