If you have an Apple device eg iPhone or iPod touch, Apple TV or even an Apple computer such as a Macbook Air, Pro or iMac then by far the easiest way (not necessarily best) to subscribe to the Gasnet podcast and receive updates automatically is using the iTunes and Podcast software that comes with these devices.
Apple has a great article to step you through the process: https://www.apple.com/itunes/podcasts/fanfaq.html
In a nutshell, using your Apple device, or Windows based PC running iTunes, go to https://itunes.apple.com/au/
This will trigger the iTunes or podcast app to open automatically and go to the Gasnet page. You then need to click on the ‘SUBSCRIBE’ button. After that the process should be fairly automatic and episodes now and in the future should download automatically.
There are many more advanced options available but that is a start.
If you would like to know more about podcasts in general then the Australian Broadcasting Corporation has a great FAQ page that answers most common questions. Like many public service broadcasters, the ABC provides many of its radio shows in podcast form so you can listen to their content, just like Gasnet, any place, any time.