As the parent(s) of a donor conceived child, you are the legal parent(s) and appear on the birth certificate. There are registries and organisations around Australia and the world that can help link your child to their donor.
Similarly, donors can find out more information about you, and depending on the donor agreement (different in each country), they are often entitled to both identifying and non-identifying information about their donor offspring. Consent is required prior to the release of identifying information. As a parent of a donor-conceived child in Australia (under 18 years), you can lodge a contact preference.