HOW TO TELL MY EX ABOUT MY NEW BF

My ex boyfriend and I have been on and off for almost 4 years and I finally broke up with him for the FINAL time in October. He battles serious depression and other issues so I’m really the person he goes to and he’s tried to even win me back. We’re also in the same friend group so we’re basically stuck together. I’ve finally started dating someone I’m crazy about and I feel like I should tell my ex before he finds out on social media. How do I tell him??