If you have found a product where the IR commands is described by the native NEC protocol, you create a TPF file that looks like this.
You can find and download an example on a complete NEC TPF file here.
Here is an example of the contents of a TPF file for the "Up" command for the WDTV Live box.
[CreatedBy]
Name=Jacob Rungwald
Email=jacob@rungwald.dk
[Product]
Manufacturer=Western Digital
Model=WD TV Live
Comment=NEC Codes
Category=SetTop Box
[Signal_Up]
IRProtocol=NEC
Pause1=65000
Pause2=65000
Carrier=38
MarkFlank=560
SpaceFlank=560
Space2Flank=1680
PresignalHI=9000
PresignalLO=4500
RepeatSignal=0
BITS=110111100110000101011111101000001
If you have the address and commands for your product as HEX values, you can replace the BITS value with the following 2 lines.
ADDRESS=856A
COMMAND=97
Then the App will generate the BITS value from that.