First you need to determine if you are really overweight, or if this is just a self-perception.

I am a fat girl overweight. I want to lose weight. How What should I do to lose weight?

Also, I agree with the others, you don't look fat; but if you're really looking for advice, cutting down on sweets, sugary foods, starchy foods (potatoes, rice, pasta etc), sugary drinks including juice, alcohol and baked goods works for me.

It depends on your age and your BMI and if you have any other health condition.

You don't look fat : )))

you are the first one call youself fat. 

You should try HIIT, there are a lot of ways to do that on internet.

I agree with everyone else, you look thin. Maybe if you're feeling flabby you just need to exercise more. Dieting is bad for your health. It messes up your metabolism, and actually leads to weight gain. The best thing is to focus on healthy eating (no skipping meals), proper exercise and sleep (sufficient sleep is also important for your metabolism). Apart from that, don't focus on yourself so much. There is so much to to do, to learn and to contribute in the world. Find something that interests you, volunteer, develop a skill.

Sometimes all of the above is not enough and the focus on one's weight and appearance is hiding a deeper issue. If you think that is the case, it might be an idea to find an appropriate person to talk to.