To embed a Visualization, you need to first make sure that it is set to be publicly visible. (For instructions on how to do that, refer to this article: Sharing your Visualization.)
Once your Visualization is publicly visible, open it up and click on the menu in the top right. In the menu select the "Share" option.
This will open up the "Share" window. In addition to buttons for posting your Visualization to social media, and a share URL, you will find a text field with the embed code, which you can copy and paste into the HTML of your website or blog.
The embedded view of your Visualization displays a smaller version of the Visualization header, although it retains all of the settings and interactivity of the full screen Visualization.
To remove the filters, search bar, and view controls from the embedded view, see this article: Turning View Controls On/Off.