In the Properties panel, you should now see appearance options for the selected artwork, which
is a rectangle, as indicated by “Rectangle” at the top of the panel. You can change the size,
position, color, and much more for the artwork you selected.
Click the underlined word “Opacity” in the Properties panel to open the Transparency panel
options. Words that are underlined in the Properties panel will show more options when you
click them.
Press Escape to hide the Transparency panel, if necessary.
Choose Select > Deselect to deselect the rectangle.
The Properties panel once again shows document properties and program preferences when
nothing is selected.