A friend code is used to connect your frame with a smartphone.
Friend codes are valid for 12 hours after they have been generated. If the code is entered within these 12 hours, the phone and the frame will be permanently connected for the future.
Here's a guide on how to generate a new friend code on your frame!
Generate a Friend Code
Step 1: Press the add friend icon in the quick menu on the frame 
Step 2: A unique friend code will be shown. The exact time of expiry will be written below the code.
If a code has expired, you can always generate a new code on your frame simply by pressing the add friend button again!
If you need help entering the code in the Frameo smartphone app, check out this guide: How to Connect to a Frame