You might want to use the Traffic View Builder resource which is by default available on the NetFlow Summary View (if not you can re-add it through the Admin > Manage Views section of the web console).
On the Traffic View Builder, select the IP Address Groups Filter and click on Build.
on the next page, Select your IP Address Group and then the router on which you want to analyze the traffic. Then if you need specify an interface. Choose your time period and click on Submit.
The next view will show you the Top XX applications used by a an IP Address Group among other resources.