In my electrical box all of my bedrooms are connected to one breaker. I have an older home so we use window AC units in the rooms. When we turn them on, it trips the breaker at times. I would like to split something off this breaker and attach it to the breaker that controls my outside receptacles. Doesn't matter which room, just one of them to allow the units to all be running. I have run a cord before to the outside receptacles from one of the AC units and had no issues so I know it will handle the load and the remaining units will run fine on the existing breaker. Any help on how I can do this myself and what I would need to do? Thanks in advance.

Unlikely you can do it yourself... outlets on a circuit are daisy chained... one wired to the next and the next wired to the next one.

And its all run behind the walls.

Rather than splitting up the circuits, which will be a PIA, you'd be much better off just running new circuits to the A/Cs.