Check out the rest of the videos in this special course: The Practical Guide To Mac Security.
If one of your online accounts has been compromised, you need to take action immediately. Those accounts, and all of your others, need to be checked carefully and you will need to contact banks and other services to protect yourself.
Check out The Practical Guide To Mac Security: Part 8, Handling Account Break-Ins at YouTube for closed captioning and more options.