The first thing you should do is to choose a healthy leaf and cut it off from the plant. The next thing you shold is to prepare a pot of good soil. By the way, you should not forget to  wet the soil well. Remember to make the soil soft. Put the leaf into  leaf the soil. Be careful not to damage it. Take a glass jar and cover the leaf with it. The soil should always be wet. Another thing you should remember is that your young plant should not stand in direct sunshine. You will be see that violet will soon develop roots and new leaves.