1. Open the Application site (See Part One: How to create the app catalog site for SharePoint online O365)
2. Click the Settings icon… Select “Add an App” from the list
3. Click on SharePoint Store on the left pane
4. Select an application to Purchase… Click on the “Try It” button to obtain a free license (30 days).
5. Clicking on the Homesite, you will see the App menu displayed on the left pane
You have successfully purchased an application from the SharePoint store.