How am I supposed to be happy?

WOW!! Though question as this can get into the existential. Live life to the fullest. Be with family and friends. Exercise and eat and sleep well. Find a hobby. Get a career that you love. Help others. Get a pet. So many parts of life to promote happiness. Now being happy and not being depressed are tow different things. So if you are depressed seek treatment with a psychiatrist or therapist or both.
It's the journey. An old saying is "happiness is in the journey". In spite of the cliche nature of that saying it has a great deal of truth in it. Happiness as a result of a goal achieved is real but fleeting. True happiness is a continuous process of doing things we choose to do and enjoy doing. One goal reached demands another goal to be set or the happiness turns into a chore or even worse, a burden. Enjoy!
You can't always be. In Happiness: Unlocking the Mysteries of Psychological Wealth, Robert Biswas-Diener stresses the importance of directing your attention to the good, checking your interpretations of events, looking back and savoring moments that made you smile, using your strengths, having a calling, balancing pleasure with meaning, focusing on relationships, and remembering it is a process, not a place. Best.