Advice

I am 18 years old and I am starting college in the fall. Some basics about me is I am 5'7 116 lbs so I am on the small side. I am trying out for the cheer team at my college but i've been pretty lazy the last year. I am trying to gain some weight but increase my cardio and flexibility. Does anyone have any app suggestions or just suggestions in general to help me. I am not good at sticking to a workout schedule either so if you can give me advice on that too I appreciate it.