introducing new birds to a flock ?

[tobij003]

I have a flock of chickens, 6 hens and a cockerel.. all a year old.. have just bought 3 hens and a cockerel 10 weeks old and need to introduce them to my existing flock.. I have split the pen so they can see each other.. I have had them 4 days now.. how do I go about introducing them.. I accidently let them together yesterday and it didnt look too good.. how long shall i keep them apart and will they be alright to mix.. I bought the 10 week old cockerel because i thought he would be young enough to mix with my cockerel without causing too much of a problem.. will they be alright ?

they are malaysian serama's ( small bantam breed)