4 to 6 months
Before starting any solid food you should make sure your child can sit up straight (it's ok if it's with the support of a high chair) and that they no longer have a tongue thrust.
To test, move a spoon towards their open mouth, if they thrust out their tongue they are not quite ready for solids. Try again soon! feel free to start a whole grain cereal or even a veggie as a first food.