Once your digi opens, click "Format", then "Position" and then "More Layout Options".
Choose "Behind text". I always do this because it lets you move the image around the page so that you can either add other images or multiples of the same one. Sometimes it's good to make a few of the same image on the page in case you make a mistake working with the first one.
Next click "Crop". This will allow you to trim any white space around an image. (All images from the Wax Fruit Company are already trimmed, so if you're using one, you could skip this step!)
Once cropped, you can then re-size the image by choosing the little checkbox on the bar that says "Size". If you crop the image closely you will know exactly the size at which your image will print.
Or, if I'm going to color with Copics, but I have some other papers I want to use for my card, I'll set my page up like this. Once printed, I use these like I would any paper for my card. The cool thing is, I can save the file and print it again if I ever need to!