How can I feel happy?

=:) Smile >24 times per day. Alone, on the mirror, while walking, smile to unknown and familiar people. Get enough sleep. Positive mental attitude.
Happy in this moment. To truly be happy, you have to be happy in this moment, instead of throwing your attention into the dead past or the imagined future. Such an internal state is likely the consequence of gratitude for the good in your life, and having skills to deal with difficulty, combined with good nutrition and healthy movement.
Could it be that... ... YOU have the answer(s) you seek? Or that YOU will be the one to find them? Ever hear this, “The journey is the destination" (attributed to Dan Eldon)? It's an important question for all of us to ask, though I think of it as a question we ask ourselves. What things and actions your life meaning? Joy? Are you seeking those things? Doing those deeds?