Settlement works very similar to closing a position. With the exception that the 'Close' button below will be changed to a 'Exercise' button under 'Expired Options'.
Pressing the 'Exercise' button will withdraw the amount in 'Current Value' to your wallet.
The 'Exercise' button will only be available if you opening a position to buy an option AND the option is profitable (or in-the-money), or if you opened a position to sell an option.
Your funds will always be available to withdraw at any time. As such you do not need to worry about forgetting to withdraw or exercise your options after settlement.