To sign morning, take your non-dominant hand and hold it down flat in front of you, so that your non-dominant forearm represents the horizon. Then take your flat, dominant hand and slide it under the palm of your 'horizon' arm, bringing it up with your dominant palm facing you. This represents the sun rising in the morning.
Teach your baby the morning sign in conjunction with the greeting good morning, or when you are beginning to teach your toddler the healthy routines that you need to establish with them every morning, like brushing their teeth, having breakfast, getting dressed, and so on.
Teach your toddler this sign in conjunction with morning routines, or when inculcating in them the good habit of greeting family members, neighbors, and schoolmates 'good morning'.