You can use a property called 'PlaceHolderText'. This will act as the default placeholder text but will automatically clear when you begin to type and re-appear when you empty the field.
To Enable the field on the text fields, please follow these steps:
1) Double click on a TextField and navigate to Field Information -> Properties and Click Add

2) Create PlaceholderText as a new text property and make sure Fixed Value, Visible and Create as predefined property are checked.

3) On the Predefined Property, select TextFields to propagate this feature across all the TextFields and click ok.

4) You should now have a new property text field in your Infigo Designer that would allow
you to populate the default placeholder text.