We are the creators of our own experiences. If we wish to have happy experiences, the Dharma tells us we have to create the causes to have those experiences. We have to abandon non-virtues like killing, stealing, sexual misconduct, lying , divisive speech, harsh speech, idle chatter, covetousness, malice, wrong views. We have to gather and accumulate merits through performing virtues and meritorious actions. These virtuous and meritorious deeds will plant seeds in our minds that will ripen into happy experiences for us.
We have also to perform acts of purification so that seeds of unhappiness, already sown in our mind-streams, will not ripen into full-blown suffering.
However, on a more profound level, happiness is a state of mind. We develop a state of mind that knows lasting inner peace and ultimate happiness, by transforming our mind in its negative state - filled with delusions like the three poisons of hate, desirous attachment, jealousy, self-grasping - to a positive one that always seeks to benefit others, that is filled with equanimity,peace,compassion, love, and joy; a mind that has cultivated bodhicitta and the six perfections of giving,moral discipline,patience, joyous effort, concentration and wisdom. Through such a mind, that has discarded ego-centrism and replaced it by a mind of always cherishing others, we will know a state of pure inner lasting peace and real happiness.