Please watch the video below.

Remember these important tips:

Use natural light. Put your work in front of a window or glass door. I've even take pictures of my work out side on the patio.
Place work flat on a table. Use the floor if it's a bigger piece and you need to be further away from it. Use the techniques shown in the video to flatten your artwork if necessary. You can also put a piece of rolled up tape on the back in each corner, to keep it flat on the surface.
Include some of the background around the artwork to avoid distortion.
Watch out for shadows. Use the sketchbook technique shown in the video. A folded piece of poster board works well too.
Use the self timer mode to give yourself time to steady and frame your shot.
Brighten and/or focus if necessary by touching the screen in the center of your work before taking the picture and adjusting.
Crop and straighten the picture if necessary.
Upload to Canvas. You can get to Canvas from your smart phone using your web browser (Safari, Google, etc) You could also email the photo to yourself and upload on your computer.

Note: If you are using an iphone, be sure to change the setting to "Most Compatible" before taking pictures. This saves your photos as .jpg files