You first of all and most importantly you have to have a boy and girl adult tamagotchi together. Use a love potion, and the code is found here, connect, play games, presents, all of that will do. They have to be 5 or older to do this.
the easiest way to mate tamas is a LOVE POTION. Once you drink it, you connect with the boy/girl tama. they have to be adults though. you connct and check your friends list, you'll have all hearts for the tamagotchi you connected with. you keep on connecting until the girl tama has babies.
First you need a boy and a girl Adult which are at least 5 years old and use a love potion [the code for the love potion is in The Tamagotchi codes link in the Site map] when you are using the love potion you go to present and they should give each other a love heart.