To set up a MAC proxy, you can follow these simple steps:

1. Click on the Apple menu in the top-left corner of your screen.

2. Select "System Preferences" from the drop-down menu.

3. In the System Preferences window, click on the "Network" icon.

4. In the Network window, select the network connection for which you want to set up the proxy (e.g., Wi-Fi, Ethernet, etc.).

5. Click on the "Advanced" button in the bottom right corner of the window.

6. In the Advanced window, click on the "Proxies" tab.

7. Check the box next to "Web Proxy (HTTP)" to enable the proxy for web browsing.

8. Enter the proxy server's address and port number in the corresponding fields. You may also need to enter a username and password if required by the proxy server.

9. If you need to set up a secure proxy for secure web browsing (HTTPS), check the box next to "Secure Web Proxy (HTTPS)" and enter the server address and port number.

10. Click "OK" to save your changes and close the windows.

That's it! You have successfully set up a proxy on your MAC. Keep in mind that these settings will only apply to the specific network connection you have configured, so if you use multiple networks, you may need to repeat these steps for each one.