L.L.
I do agree with margaret, drs say starting at 6 months with solids is best. But the baby cereal (rice, mixed, oatmeal, etc.) can be started at 4 months. The box gives you guidelines for how much to mix with the formula or BM.
I have a 5 1/2 month old and he started cereal mixed with formula in a bowl with a bottle to wash it down after every couple of spoons. He usually wants at least half of the bottle after eating. It will take a while to get past the thrusting ( pushing the food out with the tongue) but the more you offer during the day the more expert the baby becomes to chewing and swallowing. He was thrusting a month ago, now he is doing better with keeping the food in. Just don't mix too thick. The consistency of the baby food in the jar, like potatoes-sweet or mashed is what works for my baby.
Good feeding!-I offer breakfast, lunch, and dinner and put the remainder in the bottle with a decent sized nipple hole to finish. I just started adding applesauce and pears on the side with the cereal.
Dr's recommend 6 months for the baby food too, but I always started a couple of weeks early introducing a different #1 jar baby food every couple of weeks to rule out allergies. (I have 6 children)