Model the signs for your child. As a visual learner, your child will be able to understand the signs better when you do them rather than simply looking at a picture.
Tell the child what sign goes with what word. Your child will begin to understand signs for the actual meaning they create.
Test your child. Ask the child to repeat back to you the meaning of a word when you do the sign. Alternatively, have him sign a word that you select. Once he gets better at this, you can start to have conversations with the toddler in sign language.