OK, here's your solution - break it into two commands, the first to take you to your fastboot folder -
cd /Users/Matt/Downloads/fastboot
(mind the space after the cd)
./fastboot-mac flash unlocktoken Unlock_code.bin
The "./" (no spaces) means "do it from right here" and that's what you really want.
If this doesn't work, please redo the ls -lFa command right there in your fastboot folder.