Losing Body Fat - What Do I Eat ?

undereating

Hey, my weight is very low, so I don't wanna lose weight. I just wanna reduce my body fat and gain muscle weight. I would like to weight at least 4 kilos more than I do now and I need to switch my diet.
I'm going to try to eat meat and fish a lot. (I do it rarely now) Having Protein Shakes daily. And eating Protein Bars. (Have just got my first protein bombs yesterday, so yeah that's new, too)
Am I right with this ?
Now, how about fat and carbs ? I'm really confused about this. Will I gain fat, if I eat fat ? People say I can eat as much fat as I want as long as I don't intake carbs. Well and then people say you slow down building muscles if you don't eat carbs.
I'm 1.61 and I weight 46 kg.
What kind of workout should I do to get what I want ?
And how long does it take to build muscle ?

taso42

Eat around 250 calories above your maintenance level, maybe up to 500 (just configure MFP for gaining .5-1 lb per week). Target somewhere around 40/30/30% protein/carb/fat. This is a ballpark range; don't worry about hitting it precisely. You don't need protein shakes and bars if you can hit your numbers with real food. But they're ok as a supplement.

Look into a lifting program like Starting Strength, Stronglifts 5x5, or NROL4W.

Adding muscle takes time. About 1/2 lb per week (or .23kg) is about the most you can expect.