Suresh,
There are examples that ship with Modulation Toolkit for FGEN (I am using the latest versions of FGEN and Modulation Toolkit, so your findings may not be exactly the same as mine). Go to Start>>All Programs>>National Instruments>>Modulation>>LabVIEW Support>>Modulation Examples Folder. You should now see a folder called FGEN examples. In there you will find a VI called "MT nifgen AM Signal Generate.vi". This example is very straightforward and has front panel controls to specify your modulated and carrier frequency.
This example will let you test the generation with sine waves, square waves, etc. If you are wanting to generate the data from file, there are plenty of examples that ship with the NI-FGEN driver that will show you how this can be accomplished. I hope this helps.
Best Regards,
Jeremy R.
NI - Applications Engineer