Need help on Overlay!

I really need help with something specific. So I am trying to take the overlay HORSE and the overlay CARRIAGE go across the screen till the HORSE exits screen right and the CARRIAGE is on the driver’s seat. I want to enlarge the carriage, and have the character GABRIEL in the driver’s seat, moving with the CARRIAGE while idle_sit. If anyone can do this for me, I will give them credit at the end! Thank you so much for your help!