For beginners, it is better to take a copy of any simple picture. Cut the picture from the paper and stick in the glass jar. Now the painting is clearly visible from the outside of the jar.
Try to draw the outline of the picture first.
Now fill each portion with same colour paint.
Do it slowly and neatly.
For the first time, it may take time, but later it will be an easy task for you.
Once you have finished the painting, keep one thing in mind- don't wash it with water or rub it roughly. If you want to clean it, do it with a dry cloth piece. Make more paintings and enjoy your free time.