As you know the ashes on traditionally are used on Ash Wednesday. The ashes are gathered up the day before so that they can blessed in the ceremony. This period of lent is meant to change us for the better. That is why we give up something for lent to make us stronger.
This is the first day to start lent and it usually begins 40 days before easter. Every Sunday is a day when we celebrate the resurrection. The tradition is created because it represents Jesus' Forty days of fasting in the wilderness. Also, the 40 years the Israelites spent wandering in the desert after their exodus from Egypt.