By default, when a user installs an App, only that user has access to the App page and the cards in it (along with "Admin"-level users and those with custom security roles that include the "Manage Appstore" grant). If you want access, you can request access to the App page from the Appstore. If you have access, you can share access to the page the same way you share access to any page.
For more information, see Controlling Access to Cards and Pages.
To request access to a QuickStart app page,
Click More > Appstore.
Identify the App you want to add.
You can use the various filter and sorting options to locate the desired App. For more information, see Appstore Layout. You can also view a list of installed QuickStart apps by clicking Installed.
Click the App to open its Details view.
In the Details view, click Request Access.
A dialog appears with a boilerplate message you can send or customize.
(Optional) Customize the message.
Click Send Request.
Your request is sent to the App owner via Buzz.