Followed instructions here. You need some drivers.

http://0xcf.com/2015/03/13/chinese-arduinos-with-ch340-ch341-serial-usb-chip-on-os-x-yosemite/

Remember to run that weirdo kext command before you restart

For some reason I couldn’t get it to work the first couple times.

I needed to change the symbolic link a little. The thing arduino could actually see was cu.wch. not tty.ch, so just replace it with that.