Windows -

  1. Log in with your current password
  2. Press and hold Control, Alt and Delete. This will bring up some options including one to change your password
  3. Enter your current password
  4. Enter a new password

Next time you sign out/lock your account you will need to enter your new password

iOS - 

  1. Click on the Apple icon in the upper left corner of the screen.
  2. Select System Preferences from the drop down menu.

  3. Click on Users & Groups.
  4. Click the Password tab.
  5. Click the lock in the bottom left corner of the Users & Groups window.
  6. Enter your administrator password. (If you've never set one, you can leave the field blank and press OK.)
  7. Click Unlock.
  8. Click Change Password.
  9. Enter your current Mac login password.
  10. Enter a new password.
  11. Enter the new password again to verify it.
  12. Enter a hint, which will help you remember your password if you forget it in the future.

  13. Click Change Password.
  14. Click the lock to prevent further changes.

Your new password will automatically update. The next time you log out of your Mac, you will need to enter the new password.