You can use a formula field to embed a video in your form. To achieve this, you first need to enable HTML rendering for your formula field: go to the Advanced section of the formula field's settings and turn on the Render this field as HTML code toggle.
In the formula field itself (on Airtable), include the HTML embed code for your video. Please note that this is NOT just the video's link. Each video platform (e.g. Youtube or Vimeo) will have its own way of providing you with an embed code, but generally speaking you'll find this in a Share menu or similar. Once you've found the embed code for your video, copy the entire code and paste it into your formula field within quotation marks. If your embed code contains double quotes, use single quotes to wrap the embed code in the formula, or vice versa.
Usually, the embed code will also contain settings for the video player, like autoplay, or playback controls. You can modify those settings in the embed code to your liking!
You can set the height allocated for the rendered HTML by setting an HTML Container Height.