How do I make my own map for Warzone?

https://www.warzone.com/wiki/Map_Making

Like Fizzer said, see the wiki :)

Personally I found it a lot easier to get started on map making by seeing how its done rather than grasp it from text 😅
Check out Oranniss Guide to Mapmaking https://www.youtube.com/playlist?list=PLSmZ4VbaICL_Y2e6xgXkyU7jabJsh6HLs and NinjaNics tutorial https://www.youtube.com/watch?v=AkQn1pIZdY4

I also highly recommend joining the Mapmakers Discord: https://discord.gg/9xR2s5hC