You can either export from Paint as a Gif and select the background colour to be transparent (if the background is a solid colour).
Or, you can trace around the parts of your image that you want to keep, put that mask onto a new layer and delete the background layer. This way you can save it as a Photopaint file and import it into Draw.
The second option will give you a better quality image as gif's are only good for solid colours.
Paint has tools that will help select the parts of the image you wish to keep. Play around with the Magic Wand and Lasso tools, they save heaps of time.
Make sure you keep a backup copy of the origional image.
Hope that helped.