To set default version 

Open the bible to the reading pane and select the version of choice.

To switch versions or language see information here

When opening the app will default to the language you most recently used. If you want a different default, change the language before you shut down.

You must change the default in the reading page and not the verse of the day. The verse of the day will follow the default set in the reading and it will not work the other way.