Throw him in there. There will be posturing, some chest bumping, some of the hens will be horrified, and look at you, "THis is what you are adding??" Adding any bird upsets the flock, but adding a single rooster is one of the easiest adds, if there is not an established rooster in the flock. This might go on for about 24 hours, and then they will all be smitten, and if he is a good rooster you will be too.
Now roosters are a crap shoot. Things to beware of, if you have not had roosters before, is if the rooster pufffs up, raises his hackles when you come around. Or, if he crows incessantly when you are in the coup..... those are bad signs that he is thinking he should be the boss of you too. Be very careful if you have small children under the age of 5...... roosters will attack them first, almost always.
A good rooster, and they are out there, should kind of sing to his girls, he should find them treats (sometimes they are imaginary, he calls them over, and they come running) He will do a wing dance, where he stretches out a wing and kind of stutter steps around. However, roosters don't really become good roosters till they get to be a year old. Teen age roosters can be all for the perks of the job, none of the responsibilities. A good rooster is very aware of his surroundings, and if you have day time predators, he will dramatically reduce those incidents, but again, not until he is a year old.
Good Luck,
Mrs K