Found this and it worked perfectly. Doubled click on my dropdownlist and added this to my code behind.
' build the query with the product id as paramter
myCmd.CommandText = "SELECT product_name, product_title, product_desc, product_author FROM Product WHERE product_id = @product_id"
' add the parameter so the SqlCommand can build the final query
myCmd.Parameters.Add(New SqlParameter("@product_id", (DropDownList2.Text)))
' run the query and obtain a reader to get the results
Dim reader As SqlDataReader = myCmd.ExecuteReader()
' check if there are results
If (reader.Read()) Then
' populate the values of the controls
txtProductName2.Text = reader(0)
txtProductTitle2.Text = reader(1)
txtProductDescription2.Text = reader(2)
txtProductAuthor2.Text = reader(3)
End If