The locked out user can choose to reset their password, but you can also unlock their account from the Edit User dialog.
The following instructions will show you how to "unlock" a user's account so they can log in again.
1. In the Username Dropdown select Manage Users
2. Click Edit next to the user who's account you would like to unlock
3. In the Edit User dialog, uncheck the "Locked Out" checkbox
4. Click Save
Once you have saved the user, they will immediately be able to log in again.