Windows can be tiled vertically or horizontally. When tiling, always make sure that the window you want to be at the top (for vertical tiling) or at the left (for horizontal tiling) is active (e.g. the title bar immediately above the window is dark blue).
Activate the window that is to be tiled at the top by clicking anywhere in that window.
Issue the command Window>Tile>Vertically.
Activate the window that is to be tiled at the left by clicking anywhere in that window.
Issue the command Window>Tile>Horizontally.
