Hi Simon,
good question, that indeed needs a bit of explanation:
The widget (www.bing.com/widget/translator) stores the translations you make on your site with the identity of your customer ID. You will need to create and use a client ID with the value of your customer
ID. To do that:
Copy your customer ID from
https://datamarket.azure.com/account
Create a client ID with the value of your customer ID at
https://datamarket.azure.com/developer/applications
Define the matching client secret as you like. You can make one up.
Visit the Hub, and when you "get community translations", enter the value of the customer ID and the just defined client secret. You then get your community translation as an additional file in your project to train on.
Let us know if this gets you where you want to be,
Chris Wendt
Microsoft Translator