You'll then be taken to a menu screen with several options. Select "Medical ID" in the lower right corner.
It will take you to a screen where you can enter medical information. After that, you're all set.
To access the feature once it's set up, click the Home button, then "emergency," then Medical ID, and you'll be taken to the screen with all the relevant information. It only takes a minute to set up, and can be a lifesaver in a medical emergency.
It's one of those things you would rather have and never need, than need but not have.