Using Custom Fields
If the Custom Fields option isn’t showing on your Edit Page / Edit Post Screen — Click on SCREEN OPTIONS in the upper right corner. And be sure the “Custom Fields” option is clicked.
If you have never used a custom field before you will type in the name of the custom field — for this example I have called it “code”. And in the VALUE box — paste in the embed code or other text you are wanting to use as a custom field. Then click ADD CUSTOM FIELD to save the data you just entered.
To actually display the custom field on your page — in your content where you want to display it — enter the shortcode for the customfield as shown in the screenshot below. When you preview your page — it will replace the shortcode with the value of the customfield.