Obviously, we cannot train you to be a certified therapist on a website. However, here is a very brief outline. Start with the ABC model. This stands for

Antecedent – what comes before a behavior

Behavior – what the child does

Consequence – what happens as a result of the behavior.

I say, ” Eat your food.” (Antecedent)

The child moves her plate to the side, pulls the entire cake towards her and mashes it up with her hands. (Behavior.)

I say, “No, you need to use a fork.” I take the cake away, wash her hands and she gets no cake. (Consequence.)

If she really wanted the cake, this is a negative consequence and next time she may do something else.

If she hates cake and likes washing her hands, next time she will repeat this behavior.

If the child cannot speak, how can you tell if the consequence is positive or negative? The simplest way is to see if the child repeats the behavior.