How do I tone my muscles?

You cannot "tone" your existing muscle. You can gain or lose muscle and you can gain or lose fat.

Remember adding muscle isn't going to make you a she-hulk. I've lifted weights for 16 years, done a year long bulk where I intentionally put on 10 pounds, and can dead lift 2 times my body weight. And this is how much muscle I have built. 

Muscle increases your metabolism, makes you stronger, and slows the physical effect of aging-most women need to lift more, not less!