Hello Glenn and welcome to our community!
You can definitely book your tickets in advance, but the national railway doesn't release bookable schedules more than six months in advance. So, for example, for travel from January to June 2023, we expect schedules to start releasing in December 2022.
We post notifications here in the community when the national railway releases new bookable timetables. You can get these notifications via email by clicking the blue Follow button on our Train Timetables page.10
For travel in August, you can expect timetables to come out in late spring or early summer (June). Tickets are generally available even just a few days prior or the day of, and you can purchase them online at ItaliaRail6. The added benefit of purchasing online at ItaliaRail is that you'll also have English-speaking customer service if you need to make any changes or require any assistance during purchase or prior to travel.
Hope this helps! Have a great time planning your Italy travel and let us know if there is anything else we can help with.