Your baby should be able to scribble by the age of 15 months, but painting may take more time. Make sure you do not rush on this. Provide your child enough time to develop fine motor skills and pincer grasp before you expect your little one to start scribbling.
The little one will probably develop an interest in painting and drawing by the age of 18 months. Let him/her begin drawing with crayons, as they are soft and easy to hold. The child will use those crayons with his whole hand by painting with larger movements.
When the child is between two- and three-years old, he will probably be able to hold crayons or brush using thumb and first two fingers.
During initial days, when the child is still learning to draw, s/he will probably make stick figures and then describe them as members of the family. But with time the little will plan what to draw before s/he starts to draw.
You can help your baby to draw by encouraging him/her to scribble and draw from the early years. Provide your little one enough paper and crayons to draw and scribble whatever s/he wants to. You can even try giving chalk pieces to use on the floor or walls. Parents must allow children to explore their drawing abilities, even if that means they need to clean the house more often.
A fun activity for your baby will be providing leaves of various shapes and sizes and letting him/her dip it in paints or inks and pressing them on paper to see the different impressions of different leaves.
Your baby may mix colours and scribble on paper or walls. Do not stop such activities. Let the child gain more confidence and feel more independent. Using erasable crayons will make it easier for you to clean up the walls if s/he insists on using them as a drawing board.