You need site administrator permissions to perform this step.
Open a site as site administrator.
Add the add-in to the site
Click the cog icon to open the menu and choose 'Add an app' or choose 'SharePoint Connector for Confluence' under 'Apps you can add' (see below image):
Trust the add-in:
The add-in will be installed:
Check that you can add add-in parts (web parts)
Click Add a page to add a page:
Add the app part:
The add-in part should now be visible. Check that it behaves as expected and documented.