To deminish the possiblity of illness being spread from the newbies to your present flock, most will suggest you keep them seperated for a minimum of a month. Though it is unlikely they have any illnesses there still exist the possibility that they may.
And by seperated I mean as far away from your present flock as possible, not confined to one corner of your present coop/run.
Some will even suggest a smaller amount of time, but most think that the longer the time apart the better off the chances of nothing that may potentially be spread will be spreaded.
Enjoy the rirs! They are awesome layers!