Here is a helpful hint on how to add text (or more specifically contact information) to your lock screen on your Mac. You may be asking why this is useful. I believe that in the event that a warm hearted individual falls into possession of your laptop, they may be searching for a way to contact you but they are stuck at the login screen. This allows you to leave a short message saying: "If found, please contact me at ..." Here are the steps to add this:
Step 1) Open up System Preferences and go to Security & Privacy in the top row.
Step 2) Click on General and also the Lock in the bottom left of the screen.
Step 3) Enter in your administrator password so that you can edit the settings in this pane.
Step 4) Check the box next to "Show a message when the screen is locked" and then type your message into the box below it.
Step 5) Click the lock again in the bottom left corner so that no one else can edit it.
That's it! Now you can test this by locking your computer (press Control + Shift + Eject if you are using an Apple keyboard) and you should see your message written on the screen. If you have any questions or comments, please leave them below. Your feedback is very helpful!