Yes, you can.
But it is not as easy as it looks, as many people have found to their cost!
Many applications are rejected because people fail to understand exactly what the Department of Home Affairs require for an application to be ‘Valid’ and then subsequently successful.
Australian Immigration Law is complex and changes frequently. Mistakes or ambiguity on an application can lead to visa refusal.
Dept. Case officers deal with applications ‘As Submitted’.
It is not their role to prompt, assist or guide you.
Interpretation of law and procedure can at times be an issue. In these cases you need someone who knows the law and how to protect your interests. Once submitted there are NO REFUNDS or assistance from the Dept.