If necessary, put on clothes that can also get dirty. Then take your chalk and find a place where you can paint. For example, a walkway, a backyard, a playground.
Now you're ready to go.
Sometimes children want suggestions. Then you could, for example, paint an Easter nest, an Easter bunny, a meadow with flowers, a rainbow, your own family, the favorite cuddly animal, a jungle or a pond with frogs.
Then let yourselves be told what the children have painted. Thus the children learn to express themselves and you learn what the children are concerned about.
Have fun!