Swipe from the left and the current app will turn into a thumbnail; drop this and one app displays in a sidebar pane while the other takes the rest of the screen. And you can then swap these by swiping again.

Or, if you're using a keyboard, use Win+. to snap an app to the right, or Win+Shift+. to snap to the left. (Whatever the interface, you can't snap apps unless your screen resolution is at least 1366 x 768.)

You can allso snap the windows by using Windows key + arrow keys.

Left - Snaps windows to left side of screen.
Right - Snaps windows to right side of screen.
Up - Maximizes windows.
Down - Restores and Minimizes windows.