Go to your testing history page
https://services.aamc.org/mcatthx/
Enter your username and password. The next page will show your score and towards the bottom there is an option that says something like "create my own score report." Select that, the next page gives another set of instructions, but you just need to click "create score report." The score report will show your score as well as a verification code.
This way an institution can enter your verification code and score and the aamc tells them whether it is legit or not.