Fat Loss, Muscle Gain

Do you want to lose weight first or gain muscle first? It's nearly impossible to do both at the same time; weight loss requires a caloric deficit, whereas muscle growth requires a caloric surplus.

Well done for asking! That's one of the key things a lot of people get wrong

What's your height, and what kind of body do you want when you're 'done'?

As a general rule, unless you're very short, I'm guessing you're already close to or inside your healthy weight range. Because you don't have much weight to lose, and because you want to preserve/gain muscle, you'll want to set your calorie goal to a loss of 0.5 lb per week AT MOST. MFP's default macro split (how your diet is balanced between carbohydrates, fat and protein) is OK for most, but you may want to increase your protein.

That's the diet side. On the muscle gain side, you will need to do weight training, in the gym. Other people here can advise you on that better than I can.

If you are already at a healthy weight you may not want to lose any at all. Just changing your body composition from fluffy fat to toned muscle can make a huge difference to how you look and feel at the same weight. If that's the case, search for threads on recomposition