When you sell domestic shares you will be able to use the proceeds towards share purchases immediately. For international shares, your sale proceeds will be available once the corresponding foreign exchange transaction is executed. Please note that there may be a delay between the time your order gets filled and the time your foreign exchange transaction gets executed. In most cases, the foreign exchange transaction will be executed before 9am AEST the next morning (as long as it is a business day). For example, if your order gets filled overnight on Tuesday at 2am AEST, the corresponding foreign exchange transaction may get executed at (say) Tuesday 8.10am AEST. This is also when your confirmation note gets generated.
If you wish to use the funds for another purpose you will need to wait until the share sale settles. This is usually 2 days after the sale of the shares depending on the market you traded on. You can see the settlement date for trades on your confirmations found under Trading > Confirmations.