cutadapt installation location
The documentation on the installation of cutadapt is just a bit
misleading, as far as I'm concerned. Cutadapt was just installed as
a Python package. The cutadapt executable is probably in
/Users/yc/Library/Python/2.7/bin.
If that folder is already in your PATH you can just type cutadapt to
run the program. Otherwise, you'll have to type the
full path. /Users/yc/Library/Python/2.7/bin/cutadapt
As long as you're the only user using the program, it will work fine.