There are two ways:
1) Display the narrow band data in an octave display and it will be converted. You can right click on the X axis to change the format to a different octave format.
2) Use the Data Calculator to convert to octave with the Octave command.
Impact measurement data, like an FRF, can be displayed in Octave format as follows:
1. Open an “Octave Display”
2. Drag and drop an impact measurement into the display:
3. Right click on the X axis to change Octave formats
Hope that helps!