In order to see the resize and movement controls, first click on the "Edit Tiles" tab at the top of the dashboard, then hover over the tile you want to edit. Click any of the circles on the border of the tile to resize it or click in the center of the tile to move it.
Checking the "Auto-Layout" box will make the tiles dynamically rearrange to fit the window as you resize and move.
Unchecking the "Auto-Layout" box will stop all tile auto-arrangement and give you manual control over the layout of every tile. This will allow you to arrange the entire Tiles workspace to a specific width and place gaps wherever you like. *Tip: If you have a mix of different sized tiles including 1/4 size tiles, it is easier to set your desired layout by unchecking the "Auto-Layout" option for manual layout control.
To get out of editing, just click on the "x" to the right of the Edit bar and your changes will automatically be saved for you and everyone you have shared your Tiles dashboard.