There is no one standard way of doing this. Here are some options:
You could mention this information in a note about their marriage (see How to Create a Note About a Marriage) or add this as a note to their marriage event (see How to Record Facts About a Person's Life).
You could create your own custom 'Married Name' attribute (see How to Create a Custom Fact (Event or Attribute)) and record the information there. This would have the advantage that you could also associate the name change with a date, or even with a period of time (see How to Specify a Date Range, Period, or Other Complex Date).
Or you could simply add the married name as an alternative name for the person (see How to Record Alternative Names, Nicknames, Titles, etc).