water should be warm but not hot. test it with your wrist to see the temp.
water up to their front shoulders, head not in water.
put a washcloth on the bottom of the
bath or bowl you are using so he can grip onto it.
for about 15 minutes.
it takes a while for them to get used to it but its very beneficial for them so just keep him in there if he seems unhappy. its perfectly safe for them.