posrx, page-22

Clause 5.7 of the prospectus covers this off.

5.7 Selling all your Entitlement on ASX
The Entitlements under the Offer are renounceable which means that all or part of an Eligible Shareholder’s rights to subscribe for Shares under the Offer may be traded on ASX. If you wish to sell all of your Entitlement on ASX, provide instructions to your stockbroker regarding the Entitlement you wish to sell on ASX. Trading of Entitlements will commence on ASX on 28 August 2018 and will cease on 5 September 2018.
There is no guarantee that an Eligible Shareholder will be able to sell all or any part of their Entitlement on ASX or that any particular price will be paid for the Entitlements sold on ASX.

So, you have 2 choices here:

1. Ring your broker today and tell them that you have entitlements and ask them to sell them for you on your behalf, or
2. Wait until they appear in your online trading account (assuming that you have a regular online trading account), which should be Monday at the latest, and sell them online just like any other holding that you have.