"How is the Deputy Speaker appointed or elected?"

Like the Speaker, the Deputy Speaker is elected by the members of the House of Representatives at the start of a new parliament.  

The election for Deputy Speaker is chaired by the Speaker in the House of Representatives. Members give speeches nominating a member of their party–or their coalition of parties–for the role.

If there is more than one nominee, a vote is taken. Members write on ballot papers the name of their preferred nominee, and these are counted by the clerks.

The nominee with the most votes is elected Deputy Speaker. If necessary, the Speaker can vote to break a tie between nominees.  

Historically, there has never been more than two nominees. The member nominated by the government is usually elected Deputy Speaker.

diagram to help explain How is the Deputy Speaker appointed or elected?