Hi,
well, new reporting is a bit tricky I agree :-) NTA resources (charts as on normal view) can't be added to reports yet, because of some technical difficulties. However to create a table-form reports using NetFlow data use Custom table resource and then further specify which data you want to see there - now you would can access NetFlow data.
Much easier way thou, is to take one of existing built-in NTA web-reports (Report Category > Historical NetFlow Reports) and duplicate&edit it.