The first thing to check for is to see if you, or someone you know HAS digital imaging software that you can use.  This type of software usually comes packaged with all scanners, digital cameras, and also come installed on quite a few new computers.  You might already have something that will work for this assignment already on your computer. 

If you find that you do not have access to an image manipulation software, there are evaluation versions available for download that you can use for up to 30 days.  This should give you plenty of time to complete the assignment.  Below are links to some of the more popular image manipulation software and where you can obtain a copy.