...
Start in edit mode of the page or blog
Click on the "+" at the top of the page
Find "Mermaid Integration for Confluence" from the drop down list or click "View more"
Search for Mermaid Integration for Confluence in the search bar
The Insert Mermaid Integration for Confluence dialog will be opened
Copy and paste a valid Mermaid chart or diagram markdown-inspired text in the macro body. You can learn more about the syntax from Mermaid document page: https://mermaid-js.github.io/mermaid or use Mermaid Live Editor https://mermaid-js.github.io/mermaid-live-editor to edit and preview charts/ diagrams.
Click "Insert"
Save the page
...