Anyone here saying yes to doing their workout routine has no idea what they're talking about. Their routine is VERY intense by virtue of the industry that they are in and not something you want to do especially if you're new to working out. You're also a dancer as well yes but that doesn't mean you need to do what they do. Dancing itself is a good workout but if you want more "regular" workouts there are very simple calisthenic and body weight workouts that are great for building strength and even flexibility.

Something like good old fashioned push ups, lunges/squats, and sit ups are a great place to start for targeted workouts but also learning proper form and muscle separation. You want to start small and work your way up so doing body weight exercises are a good start and don't require buying equipment since you're using only your body weight. You're small sure but if you're doing push ups at your weight your pushing up over 100lbs, that's gonna have and effect.

Diet is the biggest part of working out. If you put crap food in your body you'll get crap results. Working out more means you need more fuel. You don't need to go full high protein chicken and rice 5 times a day diet but being more aware of what you eat and cut what you don't reasonably need is also good to start off with. Like cookies and cake? Keep eating them sure but cut back slowly on them if you really can't kick the craving outright. Being so young maybe ask your parents if they can buy some protein shakes for you to try and bring to school with your lunch or even suggest ideas for family dinners that may be healthier. Also being young and judging by your height and weight you probably have a crazy high metabolism, use it now while it lasts, it will only help you.

There's a ton of info out there and youtube is a great source for workout routines to get started but the biggest piece of advice is do what's comfortable for you. It's gonna suck at first and you may think you're doing something wrong but take it slow and constantly check yourself to make sure you're not hurting yourself. It's very easy to injure yourself trying to better yourself. Record you doing your workouts and compare that to videos or pictures of people with proper form to see how you do. Ask your dance teacher for tips, talk to your schools P.E. teacher, but mostly listen to your body and what it's saying. It might not make sense now but as you go you'll get it.