Window size, and fullscreen in browser:
Deselect everything by clicking outside the layout, and on the left side of your screen you should see your layout properties. At the bottom there should be PROJECT PROPERTIES. Click VIEW.
You should be able to set your Window size and fullscreen settings there.
No idea how to set to fullscreen render though.
Another way to get there would be to go to the PROJECTS/LAYERS pane in the right side of the screen, select the PROJECTS tab, and click your "root directory" (project name).
Layout size, layout margin:
Deselect everything by clicking outside the layout, and you should see the LAYOUT PROPERTIES. You can then set your LAYOUT SIZE and MARGINS.
Double-click on layout to INSERT NEW OBJECT, and on the new window, select TILED BACKGROUND. Click anywhere you wish to add the BG, then you can either create a new BG from the window, or open an existing one.
The manual helps too :)