Click on the tab of one of the files you want to edit and drag the tab to the edge of the editor frame until you see a vertical line appear in the middle of the editor frame. Then drop the tab there and you have two files to view side-by-side.
Click on the tab of one of the files you want to edit and drag the tab to the edge of the editor frame until you see a vertical line appear in the middle of the editor frame. Then drop the tab there and you have two files to view side-by-side.