Great to have you on-board.
Migration Australia WA will be in contact shortly.
This is one of the key documents a number of visa types require.
For instance if you where applying for a Partner Visa this document will inform the case officer of your relationship and show how committed you are to each other.
Now is a great time to think about these areas of your relationship and start writing down a few paragraphs, you will both need to write one.
Above all else, just be honest about your relationship. You will probably be interviewed.
Have a look at how Migration Australia charts your course to stay in Australia.