Before Mutiny can display flow data in your NetFlow tab you will need to have some additional configuration in your router or NetFlow capable core switch.

For a basic setup you need to add the following to your Cisco (NetFlow supported) device;

-----Cut Here----
!

ip flow-export version 5

ip flow-export destination your.mutiny.add 2055

ip flow-top-talkers

 top 10

 sort-by bytes

!
----cut here---- 

Then for each interface you want flows from, add the line

ip route-cache flow

eg.

!

interface Vlan3

 description Demo_DMZ$FW_DMZ$

 ip address 192.168.99.1 255.255.255.0

 ip access-group 103 in

 no ip redirects

 no ip unreachables

 no ip proxy-arp

 ip nat inside

 ip inspect sdm_ins_in_100 in

 ip inspect dmzinspect out

 ip virtual-reassembly

 ip route-cache flow

!

**Note, if the commands are not recognised then you version of ios does not support NetFlow

Also see the documents;
Introduction to Cisco IOS NetFlow
NetFlow Config Guide 

Comparison between NX-OS and IOS

Wikipedia entry for NetFlow

NetFlow tutorial