Bit by bit. Start slow, and engage with people in person when you can.
Interactions don't have to be long, but enough that you acknowledge someone, and are acknowledged by them. Sounds simple, but a lot of us know anxiety denies a lot of simple pleasures and interactions. It's tricky, and definitely a bit scary when you've been isolated for so long.
Becoming socially functional again is like building an atrophied muscle. Push too hard, and you'll deny more progress than you're able to make. Recovery in most contexts is an uphill struggle. I think it's important to acknowledge that it will be difficult, but that it absolutely is possible to find and make common ground with people again.