What can I do to tone my body?

I'm a thirteen year old girl, 5'4 and 120 pounds. My nutritionist said I don't need to lose any more weight but I should focus on toning. I want to build muscle in lose weight in my thighs, stomach and arms. What can I do? Nothing too over the top. I'd like to do these exercises before I go to bed. I'd also be eating healthy everyday. Thanks!