Appium is implemented with the server-client model. Your tests are the client, and Appium is the server.
Start Appium on your Mac. Make sure that the Android SDK and Android devices are set up on the Mac. Note the IP address of the Mac where Appium is running. Note the port that Appium uses on your Mac (default value is 4723).
On your client computer, when you initialize your driver, use the socket for Appium rather than your local machine. That is, instead of something like "localhost:4723", you want ":".
If your remote Appium server is sitting behind a firewall, or its address is hidden and handled with NAT (as is usually the case if it sits behind a router), you'll have to do some administrative work with the router. If this is the case, please look into your router's documentation to see how to handle port forwarding.