The Insert HTML Object within Muse should still allow you to add both the JavaScript snippet and input/result containers.
While we’re unable to support Adobe’s product functionality directly, if you post some additional information such as the version of Muse you’re using, and any additional context (such as screenshots of where you’re including the code snippet, and what you’re seeing when the page is published) the community can try to assist.
Also, I’ll work on updating the following article to remove the reference to the third-party Muse Themes widget if it’s no longer available. How can I use Swiftype with my site built in Adobe Muse CC?