To use markdown on Drupal, you apply it as a text filter. Your content stays as-is then gets processed (through a filter) using Markdown before being displayed on your site as html.
Install a markdown filter module
- Find a filter module like Markdown Filter
- Copy link to download tar.gz link
- In the modules area, Install a new module, Paste in the url
Enable the markdown module (in module section)
Apply markdown filter (in configuration section)
- In the configuration section, go to the Content Authoring, Text format section
- Add a new text format
- Make sure you check markdown
Select markdown as a text format in your content type
