Workout recommendations

Hi!

So I’m 22 and weigh roughly 105 lbs. I want to try and gain some muscle and tone my body a bit to help me put some weight on (doctor recommended along with diet changes).

I have no idea where to even start with at-home workouts for my age and body type. Anyone have an recommendations for places I can go online? Maybe trainers on YouTube or something?

First timer :)

Thanks!