It’s pretty simple really. Just mix the flour with enough water to get the consistency you want. So basically it shouldn’t be too think nor too watery. Then, you would separate the flour mixture into several containers, depending on how many colors you plan to paint with. Finally, you would add a few drops of food coloring into each container and whisk.
Add some paint brushes (or anything else you would like your child to use) and let them paint away!
I do want to warn you that it will get messy so just keep that in mind. I had BirBir play with it in the kitchen, so it was much easier to clean up.