Click the puzzle piece (1) in the top right of your browser. Then, click the little pin (2) next to the extension:
Open the extension (3) on any page to start generating hashtags:
You get a title and a set of hashtags. Click a tag to select it, then copy the title, the tags, or both. To change the language of the results, open the extension's options and pick one — the interface stays in English, the generated text does not.