Your supposed to quarentine him for a month. My girls took to my new roo just fine. He immediately made the head female his 'girlfriend' and then the rest kind of still followed her, and she followed him! there was a little bit of fluffing of feathers, but by day 3 of 4 he was mounting them all and they were HIS ladies!
ETA: keep him in a separate pen with shelter/feed/water away from your flock. monitor for any heath problems that might be underlying.