Some help on workouts, what to eat, etc

Hey guys,
I'm 15 and I recently started working out. I do basketball and row. As you can already tell that's a lot of cardio. I haven't been able tp put on weight no matter how much I eat and when i go to the gym I don't really know what to do. I need help getting bigger as I'm really skinny for my age. I'm 5"7, 53kg. I can post some pictures if needed.

Thanks,
Ghino