What version of Premiere Elements are you using and on what computer operating system is it running?
a. Import the video into a project with an appropriate project preset (project preset that matches the properties of the source videos).
b. One goes on Video 1, and the other on Video 2.
c. Crop each so that each occupies the right or left 1/2 the Edit area monitor screen.
d. If necessary, you can use a horizontal flip on one (see Effects).
Details can be fine tuned when details are known.