The hashtag feature gives the option to create a custom hashtag for your Experience, which will be included if participants choose to share their submissions to Twitter.
To enable your custom hashtag, go to the ‘Add a hashtag’ bar on the right side of the activity feed tab and enter your chosen hashtag.
Once you have added your hashtag, click ‘Add’. You will receive a confirmation that your hashtag has been added in the lower right-hand corner. Each Experience can only have one hashtag.