Norm
With regard to the Preview Windows Set In and Set Out
Given that you have your video in Project Assets. You double click the video to open its Preview Window and use the Preview Window's Set In Set Out for a trim.
The key (Windows) to getting the trim into Project Assets is the Panel Options/View. View has two choices Grid and List.
When the View set is for List, you just click, drag the trim into Project Assets.
When the View set is for Grid, as you hold down the Ctrl key..... click, drag the trim into Project Assets.
I think that Command is the Mac counterpart of Windows' Ctrl, so you could try the Command hold down when you are in the View Grid.
Or, you should be able to do this in View List, no hold down key.
Whatever its origin, if the source displays well in the computer and it is reading 1920 x 1080 and if it does not have any non supported Premiere Elements format, you should be in a good place for a SD or HD output.
Please let us know the outcome after your exploration of the possibilities.
Thank you.
ATR