Market App
Since ownCloud X (10.0.0) every ownCloud instance ships with the market app. This app makes it easy to manage your applications out of the box: you can install, update, and remove apps directly from your running ownCloud instance.
The market app reads the ownCloud Marketplace catalog directly over its public API. The catalog is a static, public resource, so there is no account to create and no API key to configure — open the market app and you can browse and install available apps right away.
ownCloud Instances in Protected Environments (DMZ)
To use the market app your ownCloud instance must have an internet connection. If your instance is running in a protected environment (DMZ or similar) and cannot reach the marketplace, you cannot use the market app to install apps automatically. In this case, download each app manually from the marketplace and install it by hand. Every app can be downloaded manually from the ownCloud Marketplace.