Call me lazy but:
lblTellBMI.Text = "Your BMI is: " & Math.Round(sngBMI, 2)
I.e.: Label lblTellBMI will display Your BMI is: and then append the value from a Single type variable (sngBMI) as 2 decimal points, simply by using the Math.Round method.
The Math.Round method rounds a value to the nearest integer or to the specified number of fractional digits.
Source: https://msdn.microsoft.com/en-us/library/system.math.round(v=vs.110).aspx