You can't. What Rom means (I think) is that, when you use the datasource, you can do your sorting in the microflow, but there's no sorting on runtime.
The same thing happens when using a datagrid: Database / XPath source and you can filter and sort all you want, association and microflow and you can't (same as that you can't use attributes over association with this datasource). Although I've heard rumours they're trying to remove this restriction ;-) )
A data source microflow works in order to give sorting to the listview with a microflow, indeed you will also miss the search option for users.
If you need filters for your users you should consider using the database or xpath datasource.
Otherwise creating your own custom search option would be a possibility but, is probably more work.