Important :  before updating ...

1. you must  include in your extension all the locales you  already have in the WTS (all can be downloaded as a single tar-gz archive file). Otherwise online translated work will be lost in the upload process !

2. you must also insert the relative locale line for each language in the chrome manifest file of your extension (formerly in the install.rdf file for previous FF versions) 

Then ... 

You just have to click on Submit/update extension in the Main Menu-> Web Translation System on the left side.

In the new page that will open, you have only to select your extension and then click on "Send File".
The extension is identified by its GUID, therefore if the GUID already exists it's an update !

Note: in order to use WTS the extension must contain at least the en-US locale
In case you need en-US version of your locale, send a message on BabelZilla board (Help section) in order to get a translator.
The previous version will be replaced by the updated one, but the locales and the known translators will be archived and available on request to the Admins.
You have to be logged in order to access to the Web Translation System

 

For more information, please see the other Questions & Answers