To send a "No Heroes" (or vanilla) challenge:

1. Select "Play Online", then "Challenge".
2. From the Challenge menu, you will enter your opponent's IGN (In Game Name) and use the following settings:
• Blind Challenge - No (unchecked)
• Game Type - Custom
• Game Timing - 48 Hour Turns
3. You will need to select a hero to use, but it doesn't matter which one you use (I have one named "No Heroes" to make it obvious).
4. Then select the "Challenge" button.
5. Then you will select "No Heroes" from the next screen and your challenge will be sent.