Teach your toddler the have sign when your toddler is beginning to start signing sentences and can now grasp the concept of possessing something. "I have friends." "I have ice cream."
Teach your toddler this sign in conjunction with a whole slew of objects and people that your child can have in their life. Show happiness or excitement when they begin to sign what it is that they have, so they can also cultivate a sense of appreciation and gratitude for having it.