To train you have to wait for your Tamagotchi to call you. They will call you on the hour for training such as 12:00, 3:00 etc. for training. They won't call you at every hour, and they will call you for training at diffrent times, when they call you for training is random.
When they call you for training they will have a speech bubble over their heads with a question mark inside it. When they do this go to the first icon on the bottom row of the screen and it will give you opinions for training. The training activities are in order from Smart, Cheerful to Easy-going in that order when you see them. If you want to have a smart family for example choose the first activity on the left, a cheerful activity choose the middle, Easy going is the last activity.
They always appear in this order.