Insert an image from the slash menu, or paste a URL with normal Markdown:

Any http(s) image works on a published page with no further setup.
Images stored in your Drive#
To keep the images with the content, put them in a folder called
_assets inside the published folder:
Handbook/
_config.md
_toc.md
welcome.md
how-we-work.md
_assets/
office.jpg
release-flow.png
Then reference them by name:

Markloom resolves the name to the file and serves it through its own image proxy, so visitors never need Drive access of their own.
_assets starts with an underscore, so it is never mistaken for a page.
Like every subfolder its contents are invisible on the site — except as
images referenced this way.
Cleaning up#
Images stop being referenced when you rewrite a page. The collection view
can find _assets files no page mentions any more and delete them, so the
folder does not fill up with things nobody uses.
What to expect on a share preview#
A page's share card is generated from your site's theme, colours and
title. To use your own picture instead, set image: in the page's front
matter, or in _config.md for the whole site.