Welcome to the Translator group. Please read Tasks_and_Tools, Translate_a_Page, Off-line_Translation and Translation_Workflow before starting work. You will find lots of help linked from those pages, but please ask if there is anything you don't understand. Enjoy!
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.