Vantage makes use of custom post types, so if your current theme does not, then listings will not appear in the correct location in terms of a straight theme activation. Vantage has a built in
.csv importer, so ideally you would import listings that way to ensure listings are in the right place. Other related documentation relating to importing can be found
here and
here.
Not built into the theme, but you can find an add-on in the
AppThemes marketplace which offers this functionality
here, if this is what you're referring to? Thanks.