If you have a teacher account, you should be able to see the answers to each puzzle using the "See a solution" button to the right when you're signed in. Click on that blue arrow to bring up the Teacher Panel with that button. When you're done, you can click that button again to stop viewing the solution.
Note that certain Hour of Code activities won't include this solution button. If you don't see this link on each puzzle, it's possible you originally signed up with a student account instead of a teacher account. You can email us at email@example.com to have your account changed to a teacher type!
The middle school and high school courses, CS Discoveries and CS Principles, have their own set of solutions and additional materials only for teachers. You can apply to have your account verified for access to teacher-only materials through this form: https://docs.google.com/a/code.org/forms/d/1f5QPKi3F_3nBDR8q9BcXCqixzY7SCQd7Seob0-JYizU/