If the background is all one color you can use the transparency tool on the
picture toolbar. Otherwise the quickest way is to use an editing program.
A slow tedious way would be to use the edit points. On a raster image when you
click on the edit points it will show points only on the corners, anywhere you
click on the boundary a new point will be created. You might be able to edit
points enough to remove the background. Right-click the point and you will have
options.