Baby food and formula?

Hey moms! I have a question. I just came from my son's doctor and she said we can start baby food :) My son is 4 months today. I totally forgot to ask how often do I give him baby food, and how often to keep giving the bottle along with baby food. Anyone have any advice? thanks!

SIDE NOTE: He's totally ready because he reaches for his bottle wide open as if it's a spoon, he can support his head, and he can sit supported! My little nugget even tries to reach with his mouth open for my food sometimes lol