You can insert almost anything directly into your story, no coding required. The plus sign icon that appears when you start writing—on the lefthand side of the screen if you're on a desktop, or the righthand side of the screen if you're on a mobile phone—will offer you the option to upload a photo, search royalty-free stock photos from Unsplash's library, or embed a URL.
If you choose to embed a URL, all you'll need is the link to whatever it is you wish to include. Whether that's a YouTube video, Spotify playlist, a product on a site, a link to your own online shop or blog, an ebook, a podcast episode—all you'll need to do is copy the URL, paste it where you're prompted, and hit "enter" to render the content. Be sure to save your work right afterwards so it doesn't get lost!