Model the sentence you want the learner to imitate. Keep it simple to start.
Focus on the action of the child. Say something like "Look! He wants an apple" and point to the boy when you say he, his hand and eyes when you say want and the apple when you say apple. Take the learner's hand and help him point to the "language" as you say it.
Attention is drawn to the eyes and outstretched empty hand to infer want; and to the full hand/s to observe have/has. Help the learner build cause and effect reasoning. In this image, he wants an apple because he is hungry; or he wants to eat.
Try to avoid asking questions. Questions tend to teach us to wait quietly until we are required to respond. Use Sentence Builder to develop spontaneous speech instead of answering questions. Once the learner has mastered the goals of the application, you may return to the beginning and use the application to teach understanding who, what, where, when, and how (WH)
Give the learner time to respond without a prompt. Then reinforce any utterance that follows by stating "Good talking" or other behavior specific praise.
You are shaping independent speech so don't worry about whether the response is correct. You can still reinforce and correct inaccurate utterance through modeling by stating " great talking - the boy wants an apple!"
The learning objective is spontaneous speech. You can work on accurate observations later.