To save myself time, I'm going to refer you to one of my recent blog posts adressing your concerns:
Here's the cliff's notes:
- If you're eating to get smaller, you won't get bigger.
- If you were eating and training in such a way as to build muscle, it would still happen at such a slow rate that you probably wouldn't even be aware of it happening. For a man to build muscle is a long, slow, arduous process. For a woman to build the same amount of muscle (if she's even biologically capable of it) is a longer, slower, more arduous process.
Now, for your goals, I would recommend you do some resistance training, 2-3 days per week. If you have access to a gym, try this:
Squats (work the legs, glutes and trunk)
Deadlift (work the glutes, hamstrings, trunk and grip strength)
Bench Press (work the triceps, shoulders, chest and upper back)
Overhead Press (work the triceps, shoulders, upper chest, glutes and core)
Lat Pull Down (work the lats, upper back, shoulders and biceps)
Row (work the upper/middle back, lats, shoulders, biceps and core)
Calf Raise (work the calves)
Do each exercise for 2 working sets and 8-12 reps per set. For squats, bench press and lat pull downs, perform at least 1 warm up set (more warm up sets if you need them). For deadlifts, overhead presses, rows and calf raises, do warm up sets only if you feel you need them -- most of the muscles involved will be warmed up from the previous exercise, although you may benefit from practicing the movement at a lighter weight. If you were to do 3 warm up sets of squats, your session might look like this (using arbitrary loads; this is not a recommendation of what you should be lifting, as that's entirely individual): 10xBW, 10x20kg, 5x30kg, 2x12x40kg.
For each exercise, pick a variation and load that's appropriate to your current abilities and needs. You may not be able to squat with a barbell on your back at first, so you might be doing dumbbell/kettlebell goblet squats, or even just body weight squats at first. Likewise, you may not be able to bench press or overhead press a barbell starting out, so you may be using dumbbells.
You should only need 1-2min rest between working sets, so this whole workout should take you about an hour, give or take. Do it 3 times a week, working your way through the rep range with each workout (starting with 2x8 and working up to 2x12) and then adding a little weight and starting over again at 2x8. You could safely run this progression for a few months without changing anything, and for a very long time if you cycle through different variations of the 7 basic movements.