Where do I put a custom ringtone for Facetime? (macos Sierra)

I like that Facetime Continuity allows my phone to ring on my computer. But it repeats the sound aggressively and it loops way too fast.. I created a quieter tone with eight seconds before it loops. But I can't figure out where to put it. Apparently in Yosemite you could unlock access to this folder and put it here: + /System/Library/PrivateFrameworks/ToneLibrary.framework/Versions/A/Resources/Ringtones/ But I don't see any info on where to put it in Sierra. Any thoughts?