Open the article you work on and click on the Screen Options Button as show below
Make sure the Custom fields option in checked
Scroll down to the Custom fields tab and open it
Add the name of the custom field in the form of EAxxxxxx where xxxxxxx is a name you give and put the embed code in the value field
Click on the button below to save the custom field and add the below shortcode {{EAxxxxxx}} in your article where you want the embed to appear
