If I have a video, do I need to have a custom code embedded in the iFrame, or can I add a video without it?

To add a youtube video,

1. you'd need to add an iframe element from right sidebar.
2. Next, go to the Youtube video you want to embed, click on Share button under it.
3. There will be an option called Embed.
4. Copy the embed Code and paste it onto the Iframe Editor.