That functionality is, probably, not available to the 1st generation iPad Mini
Here is the list of major new features of iOS 9 and what is available to different iPad models.
Picture in Picture and Slide Over are available on iPad Pro, iPad Air or later, and iPad mini 2 or later.
Split View is available on iPad Pro, iPad Air 2, and iPad mini 4.
Siri is available on iPhone 4s or later, iPad Pro, iPad Air or later, iPad (4th generation), iPad mini or later, and iPod touch (5th generation or later) and requires Internet access. Siri may not be available in all languages or in all areas, and features may vary by area. Cellular data charges may apply.
Facedown detection is supported on iPhone 5s or later.
Software update sizes calculated by updating iPhone 6 from iOS 7.1 to iOS 8.0 and from iOS 8.4 to iOS 9.
Two-factor authentication will initially be available to a limited number of users. Learn more.
Some features may not be available for all countries or all areas. Click here to see complete list.
iCloud requires an iCloud-enabled device. Some features require iOS 9 and OS X El Capitan. Some features require a Wi-Fi connection.
Some features are not available in all countries. Access to some services is limited to 10 devices.