My audio sample

It sounds like you have the right file, but the file is not a “program”. The file is just a list of settings that can be loaded into Audacity’s “Equalization” effect.
You need to

  1. open your Audacity project,
  2. select the track that you want to apply the roll-off effect to
  3. Open the Equalization effect (Effect menu)
  4. Click the “Save / Manage Curves” button.
  5. Import the “LF_rolloff_for_speech” XML file. See here for more details about this step: Audacity Manual
  6. Return back to the main Equalization effect interface and select the new “LF Rolloff for Speech” preset.
  7. Adjust the “Length of Filter” slider to maximum
  8. Apply the effect (press the OK button).