first you get your skills assesment from Engineers Australia( it means they give you certificate that you are a civil engineer comparable to australian standards).Engineers Australia also require your  IELTS before they  can process  your applicaton.

Then apply the migration process itself.Migration process is changing from next year.You will have to find a sponser either from employer or State government.Its easy to get state government sponsorship for civil engineer as there is a shortage of civil engineers in Australia.
There are more than 2000( my guess) nepalse civil engineers and most of thek working for govenment agencies.

Starting stalary for civil engineers is about 70,000 .