When you assign the .Value of a DateTimePicker, you need to include the date part as well as the time part. If the MySQL column has a type of TIME, then you should read that as a TimeSpan and add it to an appropriate date.
Dim today As DateTime = DateTime.Now.Date
Dim timeToSet As New TimeSpan(20, 20, 30)
DateTimePicker1.Value = today + timeToSet