If not available you need to create a new App Catalog site collection.
To add a client-side solution to your Office 365 tenant, you first need to make sure your App Catalog is available. If it was not created yet, you need to add it to your Office 365. In both cases, you need to go to the Admin portal of your Office 365 tenant and open the section "Admin Center" from the left-hand side navigation menu. Click on "SharePoint" to get forwarded to the "SharePoint Admin Center".
The following articles show you how to install the BlueBridge Glossary Webpart to your SharePoint site.