If you've added a custom embed to a page and it's not centered, following the below steps should help you to get it centered on your page.
- Identify the iframe you want to center in the live version of the page.
- Identify the ".div" class of the iframe
- Replace "iframe_div" in the below script with the selected ".div class"
- Lastly, find where the iframe has been added to the page (it's custom section), and paste a modified copy of the below script above the embed script for the iframe.
margin: 0 auto;