The integration technology used is called Garmin OneHelm.

https://www.garmin.com/en-US/onehelm

OneHelm is currently available for the GPSMAP® 8400/8600 MFD series.

The Garmin needs to be connected to the Venus-device using Ethernet. Its not possible to connect over WiFi. For the ethernet connection, a Garmin adapter is required:

1. Marine Network Cables - 6ft - PART NUMBER 010-10550-00
2. Marine Network Cables - 20ft - PART NUMBER 010-10551-00
3. Marine Network Cables - 40ft - PART NUMBER 010-10552-00
4. Marine Network Cables - 500ft - PART NUMBER 010-10647-01

1. Go to Settings → Services, and there enable MQTT.
2. Go to Settings → System Setup → Scroll to the bottom → Battery measurements. And there set up what batteries you want to see on the MFD; and by what name.

No settings are necessary. The Garmin MFDs run a DHCP server; and the Venus-devices are by default configured to use DHCP. After plugging in the cable, the Victron icon will show up after 10 to 30 seconds.

How to connect to both a Garmin and Internet? That is unclear as of now.

TBD add screenshots and so forth.