One of the best things you can do for your health is to gain muscle. This type of tissue does many wonderful things for the body.
First it increases your metabolic rate so that you are burning more calories while sitting around doing nothing. This will make maintaining your weight in the future much easier as you can eat more calories without gaining unwanted pounds.
Secondly, when you gain muscle you improve your physique. Since it weighs more than fat but is a denser tissue, the scale may actually go up but you will look smaller! Plus you will have a new, curvy appearance to your body.
If you gain muscle you will also decrease your chances of getting injured because your body will be more prepared to deal with lifting heavy objects. If you are weak then even lifting the groceries out of the car could be challenging but if you are stronger, you won't have this problem.
In order to accomplish this goal you will need to lift weights, preferably a minimum of three times a week. Some people will choose to lift 5-6 times a week but it all depends on what type of body split you are using.
You can do a full body workout 3 times a week, taking a day off in between each session or do a upper/lower split which is normally done on a schedule like Monday and Thursday for upper body and Tuesday and Friday for lower. Then you can have Wednesday and the weekends off to rest.
The most important thing to remember when trying to achieve this goal is to lift heavy. It is essential that you place an overloading stimulus on the body or else you are not going to see growth.
Also be sure you are eating enough calories to supply the body with all the building blocks it needs to develop this new tissue.
If you follow these tips and stick to your regular workouts without fail, you will see results in no time!