Instructions
Go to the DigiColiseum and speak to the Kudamon behind the counter in the entrance hall. Select "Digi-Matching" and follow the on-screen instructions to breed your Digimon with another player's and create an egg.
Return to your Farm and place your DigiEgg there. If your Farm is full, transfer an active Digimon into the DigiBank to make room.
Examine the DigiEgg and it will tell you hatching conditions. The conditions are Experience-Point related and require experience of one or more species.
Go to the Farm Shop and purchase a Terrain Board with bonuses that match the species of your egg. The Terrain Boards will cause Digimon standing on them to gain correlating species experience points at an enhanced rate.
Continue playing the game and return periodically to speak to your DigiEgg. Speaking to the egg once the conditions have been met will cause it to hatch.