You need some kind of "Virtual MIDI cable" to connect two MIDI apps with each other. macOS / OS X doesn't come preconfigured with such a connection, but it is pretty easy to set one up. Just follow these steps:

1. Launch the "Audio MIDI Setup" of macOS
2. Open the "Window" menu and click on "Show MIDI Studio"
3. Double-click on the IAC Driver icon
4. Activate the "Device is online" checkbox
5. You can rename the Device Name if you like, but please only use characters that are available on an English keyboard! "IAC Driver" is fine, "哈佬" not so much.
6. Create a new port by clicking on the "+" button below "Ports" (see the screenshot below). Again: Name the port as you like, but only use English characters (the second port name in the screenshot wouldn't show up in the feelyoursound.com software, for example).
7. Restart your DAW and your feelyoursound.com software
8. Set the MIDI Input of the DAW to the newly created MIDI port
9. Set the MIDI Output of the feelyoursound.com software to the newly created MIDI port as well
10. You're done!