A new, community-hosted Unreal Engine Wiki - Announcements and Releases - Unreal Engine Forums this is what you want.
Do stuff in that tutorial.
- Now place second camera in your scene and toggle it on when minimap is on.
- Set script that sets minimapcamera’s location to be same as your pawns location (except Z is higher)
- Draw the minimap with widgets on top of your screen, use transperency shader so you can actually see through the minimap.