Hi erialcrobo,
If you want to insert clipart into a 'shape' object (which can include a
circle):
.. right-click on the object
.. click 'Add text'
.. now use Insert|Picture|Clipart, etc to insert the clipart into the shape.
If you have a circle that is a bitmap image, you can't insert clipart into
it. You can, however, insert the clipart into document, the use
Format|Picture|Layout|Square, after which you can drag/reposition the
clipart over the bitmap.
Cheers