Your best bet is to buy 6 young fish and grow them up together until a pair naturally form.
Depending how old the fish are when purchased will determine how long it will take for this to happen.
I assume you will start with 2 to 3 inch juveniles.
If this is the case expect your first spawn within the first year.
Sexing these fish is quite hard,up until the fish reach around 6 inches.
At this size the male will develop a more masculine head and will probably be a little bigger than a female of the same age.
Males dorsal fins will also rise a little more steeply towards the end of the fin than a females will.It is also said males will develop blue eyes.
In the picture below you can see that the two fish at the bottom are male,the two at the top female.You can just see the difference in head profile.
In this picture the male is at the front.
I would recommend raising youngsters and not try to find adults.They may not be compatible.
It is also very rewarding to see fish grow up pair off and raise fry.
