How to wire side camera and make come on when blinker is turned on

No idea. But a 2023 860! Nice!!! I'm jealous!!!

 

I would explore wiring two relays from the turn signal lever/switch, one for each direction. Anything spliced into the lighting system is going to pulse off and on, so you have to find which wire is going to have constant current going through it when you move the lever.

https://www.amazon.com/labwork-Signal-Switch-20797838-2005-2012/dp/B07X83H2TX
It's a switch for older models, but it should be a similar concept.

I would find which color wire is supplied a constant voltage when actuated up or down, then splice a wire to a normally closed relay that goes to whatever controls that side's camera. Do the same thing for the opposite side. I'm not sure how the camera communicates with the screen, but it's going to play a part in how you wire the other side of the relay.

There might be a less complicated method, like just a switch instead of a relay. I would think it is better to isolate the camera side, so if any issues come up it's not on the same line as the turn signal current.

 

You probably don't need a relay or switch. The switch is integrated into the lever. As long as the wire normally has no voltage, and supplies voltage when in that position.

 

DVR should have signals input plug to connect brake light or turn signals. Camera recording all the time when you turn signal or push brake pedal the event will be recorded under video. Special viewer program needed.
Ask DVR customer support or refer to manual.