You can't, trusts are completely secret. When you set up a trust (in Vic) all that happens is that the State Revenue Office stamp the front page of the trust document. They don't take a record of things like the Settlor or Appointer's name, who the Trustee is, etc. You just pay your $200, in cash if you like, and you're away.
The ATO will have a record of who the trustee is, required when applying for a TFN, but they ain't going to tell you...unless you're another govt department or possibly an overseas tax authority.
If the trust owns a property with a mortgage then the bank will also have full details of the trust, but again they aren't going to release that to anyone.