Depending on the device that you use as a remote you should see an empty extensions list in Settings→Extensions, or the Extensions tab is missing if you are on a phone. Both are intentional, unfortunately extensions are not available in the phone UI 
If you are looking at an empty list, that’s because extensions have to be installed separately (hence the name). To install the CD Ripper extension you need a Linux system, e.g. a Linux distribution on a PC or NUC, or a Raspberry PI.
Some references with more information:
If you have more specific questions, feel free to ask.