Closing an image on the canvas is not necessary in BeFunky. If you have an image open on the canvas, you can choose one of the options under the Open menu at the top of the app to open a new image or project to work on. Opening a new image/project will close the existing image on your canvas and open the new image.
If you'd like to clear an image from the canvas at the end of your session, you can click the Reset button located in the lower right corner of the app to reset your canvas.
Looking for more inspiration? Check out another tutorial:
Get to Know the Photo Editor
Introduction to the Image Manager
Saving and Sharing
Opening Saved Projects