You’re never too young or too old to learn to see like an artist.  A great way to start is to bring something from outside to paint or draw.  Something a little complicated works best, like a flower, a pinecone, tree bark, or a shell.  Then set up your art materials, but there is one thing you must do before you start to paint or draw.  Preschoolers are right at the age where the brain starts to learn symbols for things.  Examples of drawing symbols rather than the actual objects would include the sun drawn as a circle with lines going out, or a house drawn as a square with a triangle on top.
Your job is to instruct your preschooler (and yourself) to stare at the actual object for a while before painting. We’ll use a flower as an example. Here are some questions to help your observations: How many colors do you see? What shape are the petals, do they change anywhere? What do you notice about the center? How long is the stem compared to the blossom? Lastly be sure to stop while in the middle of painting and look at the flower from time to time. If you don’t stop and look the symbol part of the brain will take over and complete the job! Like any other skill, the more you observe and paint or draw, the better you get at it and the better you get at seeing the world around you.