New blocks can be added by inserting a title and then clicking on the + Add new block button from the Blocks page (see the image below).

A new page will load allowing the user to define the content of the new block.

If you have a block created and you want to translate it into other languages, open the selected block and click on the Translate button.  Tick the language that you want your block to be translated to and click on Continue.

On the lower part of the page, a window with the translation will appear. Please check it and if it is correct click on the Create blocks button. 

After that, the confirmation message Content modified successfully will appear and your new translated block is created.