Now that we have enabled external sharing in Office 365 and SharePoint Online, itâ€™s time to secure external sharing capabilities! There are couple of ways to secure external sharing and ensuring that external users can only access an inviting organisationâ€™s content that they have been invited to and not have access to any other assets or content.
Uploading a SharePoint Add-in to a corporate add-in catalog is as easy as uploading any file to a SharePoint document library. You fill out a pop-up form in which you supply the local URL of the add-in package and other information, such as the name of the add-in. (Reference Link)