To install, just go to the webpage at the address posted above, and follow instructions on that page.
Basically, on that page you need to scroll down and download the app corresponding to your device. The package is 2.3.1 at present.
Once you have saved the package on your PC, follow the instructions from step 1 through step 4 to install it on your device (not the instructions “how to update Sync”, but those “how to install Sync”).
Once you are done, use a browser to go to the address of your device followed by :8888, like http://192.168.1.132:8888 and there you will find the web GUI of the Sync app running on your device.