As a Google Apps admin you can push our apps to the users of your domain to facilitate access and enable them directly for all your users. We will details all the way you can use to let your users access our applications.
When we create a domain license for an application, all users of the domain will have access to the application without seeing the paid option with a direct access to all features. For example if you buy a license for the domain ez34.net, all users with an email @ez34.net will have a direct access to the application.
It is completely transparent for your users.
You can share the link of the Chrome Web Store listing of the application and let each users install it. This is the simplest way to grant access to our application.
For more details, on how to install and access an application from the Chrome Web Store, you can share this article : install & access chrome application.
As a Google Apps admin you can force installation of the application for you domain. Refer to this documentation on how to manage Chrome App for your users : help page. There is multiple articles, read carefully.
All users will automatically have the application installed on their chrome session if they are signed in to chrome.