For the following steps you need Confluence Administrator permissions.
Installing the App
The app is available at the Atlassian Marketplace. To install the add-on, log into your Confluence as a system administrator and navigate to the "Find New Apps" tab of the Universal Plugin Manager (UPM) in the global administration. There you simply search for "SharePoint Connector for Confluence" and make sure you selected "Cloud" in the "Hosting Options" dropdown. You can find the UPM via the menu entry "Find New Apps" or similar. For more details about managing apps please refer to the documentation provided by Atlassian.
Image 1: SharePoint Connector for Confluence at Atlassian Marketplace (click to enlarge)
Licensing the App
The add-on needs a valid license, otherwise features might not work. The license model is the same that Atlassian uses for its products – for further information see the Atlassian documentation.
To try or subscribe to an app, click the Free trial button next to the app ion the Atlassian Marketplace.
If you don't terminate the trial within the trial period, a subscription for the app kicks in. Trials last for a month from the start of your next billing date. After starting a trial, you can stop it from the app administration page.
Image 2: Add-on Manager (click to enlarge)
Although you can re-enable the trial within the original trial period, you can't try it again beyond the original trial period. At that point, you can only subscribe to the app from the Manage apps page.
If you'd like to cancel your subscription to an app, go to Settings > Manage apps from the Confluence sidebar, then click Unsubscribe.
Updating the App
You can update your app to the current version directly in the Confluence administration. Go to "Manage Apps" and open the app. Click the "Update" button.