Back over to the layer tab.
Turn off the layer "Layer Shadow" (Or maybe "high horse" ?)
The eye icon or remove tick from box or right click popup.
Now we can see the layer underneath (in the editor)
If we run the project again (F5) we still get the black screen and coloured squares. This layer visibility only affects the editor.
Lets turn back on the layer visibility in the layer tab and also unlock the layer by clicking on the padlock icon (but which one ....)
Left click on one of the squares - did you notice the properties bar change ?
Lets make the squares bigger ! (I don't know how much more excitement I can take....)
see in the properties bar one of the properties is size ? Lets click it and change the 50,50 to 150,150.
Next to the size there is a small plus (or maybe a minus) sign this allows you to see the x (width) and y (height) of the sprite separately.
You can also alter several sprites at once - lets select them.
A couple of ways to multi select. Left click drag a selection box around both coloured squares or left click one then shift left click the other.
Now in the properties bar change both x and y sizes to 200.
You will probably find them overlapping ?
Lets tidy them up a bit.
While both squares are selected right click and from the popup select align/edges/top. This will align the top edges together.
With both squares selected left clicking and dragging inside one will move both together.
Move then (individually) until they are not overlapping and you are happy with the positions. (do not forget the right click align is there to be used)