I don't know about Blogger as mine is on Weebly. But, I assume you've gone to the highest level of your site on Nabble and selected Options/Embedding Options. That should get you a screen that looks like the one below. (I scribbled through part of the code for my protection.)
For Weebly I copy the code and paste it into an embed widget on a page on my site. And then I make sure that HTTPS is turned off on my site. However, while security is supposedly and option now, I haven't tried it and therefore can't tell you how to do it.