Waeco MT 350 Installation Problems - Urgent!

Hello,

I was just about to install my Waeco MT 350 fridge. It wasn't really a problem; I found all the cables right away and soldered them neatly!
Only I am having a problem with the voltage/power supply of the system!
Where do I get the positive connection for the battery, where do I get the positive connection for the downstream device, and where do I get the positive connection for the ignition?
I've tried connecting everything to the positive cable that goes to the radio, but when I press the remote control, nothing happens except that the remote control light flashes briefly!
What could be the reason for that?
Is the radio transmitter new? Does it need to be re-paired/re-coded?
I urgently need help because my car is in the garage with all the wires scattered around the footwell, and I wanted to drive away today!

Hello.