Please check the text is red on the https://yescrowd.optus.com.au/ page.
Once you read it you will understand that you need to contact Optus via myapp of twitter or phone or some other way.
I'm not sure that Optus offer a yearly summary. Like most other utilities, they provide a Tax Invoice for each billing period (generally monthly) but not a yearly summary.
You should be able to see these in My Account once you click on Bill and Payment history on the right hand side. You can view and/or download your tax invoices for whatever period you like (in my own account, they go back to 2015).