As soon as you receive your eCoE (electronic Confirmation of Enrolment) from the ANU by email, you should purchase OSHC (Overseas Student Health Cover). You can then apply for your student visa. If you have any questions about the eCoE, please contact the Bell School (bapa.bell@anu.edu.au).
Both ANU and RU are unable to answer questions about visa applications, including how long it takes for a visa to be issued. Please check the following website on your own. Since December 2023, when the Australian government announced its migration strategy, student visas have been subject to stricter scrutiny. We have heard that in some cases, the process can take two to three months, so we recommend that you understand the situation and apply as soon as possible.
Department of Home Affairs, Australian Government > Immigration and Citizenship > Student visa