I integrate at 4-6 weeks...after they have been brooded amongst the flock for a few weeks. Chicks get moved to a separate coop section about 1 week after hatch. Their heater is in there and there's a separate run too.
Here's how I do it...
Pics of your coops and runs might garner some specific suggestions.
But here's some tips about.....
Integration Basics:
It's all about territory and resources(space/food/water).
Existing birds will almost always attack new ones to defend their resources.
Understanding chicken behaviors is...