Teenager hoping to get better at HIIT workouts and not wanting to quit!

Hello everyone! I'm Kate and I'm 15 years old. It's my second day of the first round of FB Fit. My goal with this program was to tone my body and become stronger. I'm not overweight, but I would just like to become more confident and fit, as I have some stomach and thigh fat I would like to tone. I am also not very physically fit/strong, and would like to change that! However, the HIIT workout on the second day of FB Fit is very hard for me. I got to about the 10 minute mark, and was dying!! I had to stop. I'm just wondering if there's any advice from anyone that helps to get through the workout, or maybe easier alternatives. Should I have chosen a different FB program to invest in? I looked into the lower impact option, and I think that was a bit easy for me.. should I just do the lower impact ones to build endurance for now? I truly don't want to give up on this 8 week program, but right now I'm just not at the level of the videos. Please help!