I have send the mail to TRA and asked them the same questioned. They replied me with this answer.
The TRA Migrations Skills Assessment program is an assessment conducted by TRA on information you provide in your application and on your supporting documents. To complete the application form, you will need to print and complete the form by hand and post to TRA with certified copies of the required supporting documentation and the application fee. Once your application is received by TRA, you will be provided with an acknowledgment letter which will include your TRA Reference Number. Information on the application process, including the TRA Migration Skills Assessment Applicant Guidelines and application form is available on our website Home Page under the ‘TRA Migration Skills Assessment link’
You will find TRA Post address on TRA Guidelines. Hope this help
Trades Recognition Australia
Department of Industry
GPO Box 3022
CANBERRA ACT 2601