When to introduce new chicks?

I got 3 silkie chicks today, they are just starting to feather (I believe the person said they were 5 and 6 weeks old). When will I be able to introduce them to my flock?
Obviously it will be awhile, they are still tiny and can fit through the holes in the front of my coop. But I'm curious as to how long it will be before they are old enough/big enough to be introduced to a flock of 6 full sized hens and possibly a rooster (I am getting rid of him).