Here's how you can add various types of media to your posts.
To add images:
Drag and drop them into the editor, or upload a new file.
To add GIFs:
Drag and drop them into the editor, or upload a new file, just as you would any other image.
To embed rich media (e.g. YouTube and Vimeo videos; Soundcloud, Bandcamp and Spotify tracks; Instagram photos, and tweets):
Copy-and-paste the URL into the editor (using embed codes won't work). The embeds will appear like magic.
To add a banner image:
From the post editor, click "Set a preamble for emails", above your post title. You can upload a banner image on the next page.