To make it a little easier, it will depend on what you want to do:
1) If you simply want to purchase as many (or even more) new shares than you are entitled to, then wait for the prospectus to arrive in the mail and follow the instructions. The Offer closes end 12/09/18*, so you'll have comfortably 1 week to act after your receive it in the snail mail. I strongly suggest not leaving your acceptance/payment to the last minute, though.
(*Subject to not being extended by the Directors.)
2) If you don't want to participate and you are not interested in trying to extract any value that might be had from selling your Entitlements (not really aimed at you, but anyone else reading this), then simply do nothing. Your total shareholding will remain unchanged. Only your percentage of ownership of the entire company will change/dilute (by a little more than half).
3) If you want to buy/sell any Entitlements, then you'll need to do so when the short-term window for Entitlements trading is active (i.e. the period between 28 Aug and 5 Sept). Your broker should be able to assist.
There are other scenarios available too, which are all covered (including those mentioned above), in the Prospectus document, which can be downloaded and read right now, in preparation for when it arrives in the mail.
Naturally, all of the usual disclaimers apply.... None of this should be construed as advice. Consult your accountant or financial advisor (eek!) that. Er, maybe best to just stay with the accountant...
(20min delay)