To be happy and to bring happiness into your life you need to know what it is. For each of us this can be different and may even be tangible or intangible. You may already know what makes you happy and some of us may not.
If you already know what makes you happy then your focus should be to eliminate the things in your life that takes that happiness away from you. This may be people you associate with that consistently bring your mood down. It may be job you dont like going to. It could even be a problem in your life that needs to be dealt with that you keep putting off. Whatever brings your happiness level down you must first acknowledge it, accept that it is an issue, then you can properly address it. Once this is done you can focus on brining your happiness to the forefront of your life.
For those of us that have trouble identifying what brings us happiness that is our first task. We must take the time to look at our life and decern what makes us happy. Think about your day, what do you do that you take enjoyment in? Is there a specific activity you enjoy doing? Is there a person you enjoy being with? What makes you happy? Once you figure out what makes you happy, you should spend more time doing it. This should go without saying but alot of people tend to neglect themselves and what makes us happiest.
Take some time to really think about what makes you. Look at yourself, look at your life, and be happy.