Welcome to the Translator group.You will notice on Translation_Workflow#Language-specific_guideline_pages that a Team Leader exists for your language. While there is no requirement for you to contact your Team Leader, it would be appreciated if you do so. Please read the various Help pages mentioned on Working with Languages before starting work.
The option to export messages for off-line working is found in the first combibox of the page you reach via the Translate this Page link. When you work off-line we ask you to send your first set of messages to me for uploading. Once it is confirmed that they upload without a problem you will be told how to upload them yourself.
Please ask if you are unsure about anything. Enjoy!