To control Elgato Key Light via Elgato Stream Deck, you will need to download two things:

• Elgato Stream Deck software version 4.0 or later
• Elgato Control Center software version 1.0 or later

You can get those here:

https://www.elgato.com/downloads

Then, when you launch Elgato Stream Deck software, go to the Control Center section.






You will find the Elgato Key Light controls there:

• On/Off
• Set Brightness
• Adjust Brightness
• Set Temperature
• Adjust Temperature

Drag those Actions to the left, on the keys you prefer.  Setup up each Action according to your needs.