I've just started this route. This pdf will explain your question
http://www.engineersaustralia.org.au/sites/default/files/shado/About%20Us/Migration%20Skills%20Assessment/migration_skills_assessment_booklet.pdf'>http://www.engineersaustralia.org.au/sites/default/files/shado/About%20Us/Migration%20Skills%20Assessment/migration_skills_assessment_booklet.pdf
Everything else you need should be here
http://www.engineersaustralia.org.au/