I find myself in the same position in that I had a line layout of a town and regional area that I wanted to use some styles available in CC3 and I had the same problem...Bought the prog (not just THIS goal in mind, but was one of the deciding factors) with some add-ons and couldn't figure out how to do just what you are trying to do.
Just now I think I might have figured it out...Under the DRAW menu there is a "Insert File". Clicking that opens a window that allows for choosing a file or browsing to find one. Go looking for the file that you want, click Open. you will get the cross hairs for you to click the top left and the next click anchors the bottom right of your image. I suggest that you set your work space to the same size as your image, or at least the same proportions...Also note that CC3 will only import certain file types so make sure that your image is in one of those formats.
That SHOULD get your image into CC3, but I haven't tried doing anything with that image yet so that is as far as I can guide you on this. Hope this helps you out some.