These settings depend on the site. A WordPress.com site without plugins and a site with Jetpack use different activation paths; an arbitrary self-hosted WordPress installation may need its own Markdown plugin.
Enable the feature for the site you are editing
For a WordPress.com site without plugins, open Settings > Writing, enable Use Markdown for posts and pages, and save.
On a plugin-enabled site covered by WordPress.com's instructions, open Jetpack > Settings > Writing. Under Composing, enable writing posts or pages in plain-text Markdown and save if the save control is active. Markdown for comments has a separate setting, so changing the post setting does not settle the comment workflow.
Make these changes only where you manage the site. If your account cannot see the setting, ask the site's administrator which Markdown implementation is installed rather than installing another editor to work around it.
Keep a short notice inside one Markdown block
In a draft post, add a block with the plus button and search for Markdown, or type /markdown. Copy this original practice notice into its Markdown tab:
## Studio opening hours
The studio opens at **10 a.m.** on the practice date.
- Bring your reservation number.
- Check in at the reception desk.
Ask for the room labeled `Studio B`.
Replace the fictional opening time, directions, and room label before using the notice. In Preview, expect a section heading, a bold time, two separate list items, and a literal room label. Return to Markdown to revise a word. Keep the punctuation with the source you intend to maintain.
Check which Markdown features the block supports
WordPress.com documents the block as following CommonMark, without Markdown Extra support. The Classic Editor can use Markdown Extra, so a feature that worked in an older editor may behave differently in this block.
Start with the heading and list above when diagnosing a problem. If those render but a more elaborate construct does not, isolate that construct in a draft. Avoid assuming that a table copied from a GitHub README must have identical support here.
If you need to edit existing HTML, use the separate WordPress HTML editing workflow. A Markdown block expects Markdown source; switching the whole post to the Code editor does not enable Markdown parsing.
Preview the post with its actual theme
The block's Preview approximates the rendered content. Your theme influences its appearance, so open the full draft preview as well. Check the notice at a narrow width and confirm that the opening time stays beside its explanation.
Save and reopen the draft before publishing. Confirm that the block still contains the Markdown source you meant to maintain, and that the rendered notice contains the correct room and time. Publish through the site's normal review process after those details are settled.