I’ve just had a quick look on Google, and found that FTR Audio is a propitiatory format. There is a free player available here: https://www.fortherecord.com/download-ftr-player/
Audacity will not be able to open the FTR Audio files, but if you play them in the free FTR Audio player, you will probably be able to record them in Audacity in the same way as recording any other audio that plays on the computer. See the “WASAPI loopback” section on this page: https://manual.audacityteam.org/man/tutorial_recording_computer_playback_on_windows.html