This is plugin is meant to help self-host asciicasts on your WordPress site. If you are simply wanting to include asciicasts from asciinema.org, then take a look at their embedding guidelines.
This plugin adds a shortcode to help display the Asciinema player. Once installed, you can add the JSON formated terminal sessions to the ‘asciicast’ directory under the ‘uploads’ folder and reference them using the shortcode. The below terminal session is displayed with:
[ asciinema src="wp-asciinema-hello-world.json" speed="2" ]