Step 1: Add an Application Catalog in O365

The first step involves creating an application catalog and uploading and registering the app. 

NOTES:

• Creating a new app catalog is not mandatory if you have an existing app catalog you'd like to use.
• New O365 tenants do not have an app catalog so you'll need to create one.

1. Login to your O365 tenant using the account using your Global Admin permissions. 
2. Go to the Admin section.
   
3. Choose Admin centers > SharePoint. 
   
4. Go to More features > Apps > Open. 
   
5. On the Apps page, click App Catalog.
   
6. Select Create a new app catalog site and click OK.  
   
7. The new App Catalog window displays. Enter a Title for the application, Web Site Address, and select one Administrator. Click OK. 
   
8. Open the App Catalog site. Go to the SharePoint admin center and click the App Catalog URL. 
   
9. Click the Site Collections link. When the properties window appears, click the site collection link.
   

Continue to Step 2.