welcome to reefcentral. I think you might learn more in the newbie section. But let me throw in my two cents.
First there are to many ways to do it. But let me tell you about the sexes. All clowns are males when born. If you have a group of two or more the biggest , will tend to pick on the smaller fish. Well that big mean fish will most likely turn into the Female. All males can turn to females but females cannot turn back in males.
Don't get a big fish to start with,especially if you think its a female. big fish like to take over their territory. So if you throw in a small fish later it will most likely kill it or fight it until you pull him out.
Go to a fish store find a group of clowns, buy the smallest one of the group(most likely no the big mean female). Put him in your tank a week or two weeks later, go back to the fish store and buy the biggest one in a group. Since the big fish is put in later it might not be as aggressive towards the little one because its not his territory. After a while you might see them hang out together. I'm sure you will still see the big one nip at the little fish but thats natural. The big fish will later let the little one know whos the boss. And the little one lets him know by swimming sideways and acting like he is having a seizer. he will start shaking towards the bigger one, thats how he tells the big female he doesn't want any and backs down. Be careful though what works for someone might not work for someone else.