In case that your blog exists in more than one cultural version, you will get the following dialog displayed after blog type selection (step 4) when registering your blog account.

 

 

In the dialog, you need to choose which cultural version will the account be registered for. This means that you need to register one dedicated account for each cultural version of your blog.

 

Page url: http://devnet.kentico.com/docs/devguide/index.html?metaweblog_api_multilingual_support.htm