The Cicada Australia Inc. membership form is now available from the web-site. There is a separate menu item above "Members" which takes to the download link, where you will find a printable version of the form for your convenience.
It is only $10 for a life-time membership, which gives you access to a posted copy of the NSW "BUZZ" newsletter. as well as the opportunity to participate in events hosted by CICADA NSW. Note that "BUZZ" is not available for overseas mailing.
There are also links to the other CICADA groups throughout Australia, which you can find by choosing the State Groups menu item.