All it takes is putting them up on the roost one or two nights - they figure it out really quickly! If these are your first chicks, I wouldn't worry about it - they will start roosting when they're old enough. The only reason I have to train mine now is that I have a LOT of birds and the juveniles get intimidated by the older birds and lack the confidence to compete with them for roost space. But once I put them up there for a night or two, they get the hang of it and after that they get up on their own. If you add chicks in future years, you might need to help them gain the confidence but without older birds to intimidate yours, they will start roosting when they're ready, without any training.