How to Set a the Message in an AlertDialog.Builder

public AlertDialog.Builder setMessage (CharSequence message) was added in API level 1
Set the message to display in an AlertDialog.
Returns: This Builder object to allow for chaining of calls to set methods

1. Create an AlertDialog with Supplied Arguments

2. After your AlertDialog.Builder is instantiated in step 1, add the following line to set the message.  

myAlertDialogBuilder.setMessage("This is my message to notify you.");

3. Compile and run!

Next Recommended Article: How to Set the Title in an AlertDialog.Builder

Resources:
http://developer.android.com/reference/android/app/AlertDialog.Builder.html#setMessage(java.lang.CharSequence)