You cannot generate one report for two separate periods in MoneyWiz. The report period needs to be a range. So you could generate a report from January 2014 to January 2015, broken down monthly, and then just look at the two January months you'll see, ignoring other months.
I understand that you would like only to see two January months - but this is not currently possible. We don't have anything like that on our to-do list at the moment so I'll leave this ticket open to see how many votes it gets!