If you paste a graphic object into a WP document with the text tool active, the graphic will be treated as if it were a piece of text. You can tab it to a new position, but you can't click on it with the arrow cursor and reposition it.
If you select the arrow cursor before you paste the graphic, it will come in as a graphic, with handles so that it can be resized or moved.
If the graphic is pasted using the arrow cursor, you can position it over text. You can change the stacking order and have the text appear over the graphic by using the Move commands under the Arrange menu.