How can I contact Microsoft to discuss using old IP

I’ve had very little luck finding an answer to this. I’m interested in creating a game based on an old IP that Microsoft gained in the Activision/Blizzard acquisition. Publicly, Microsoft has said they were open to such ideas, but I haven’t been able to find a way to start a conversation!

I anyone has some direction they are willing to share, it would be very appreciated.

:)