Thank you for your question, Lucinda! Government departments communicate directly with the minister responsible for their department. The minister might choose to present an idea from the department to Cabinet for discussion. If Cabinet agree to the idea, a bill is drafted, and the minister introduces that bill to the Parliament. Resources are allocated by the government to the department and are explained in the Budget papers each year. Budget bills are considered by the Parliament and must be agreed to before resources can be allocated.
The process of making and passing a bill depends on how complicated, urgent or controversial a bill is. In the event of an emergency a bill can pass in a day. However it is more usual for it to take weeks or months in order to give the Parliament time to consider the bill carefully. For more information on bills have a look at this House of Representatives Infosheet on making laws.