If you want to use Brightspace on your mobile device, you can use Pulse, an app made by the creators of Brightspace. It is available through Google Play and the App Store, for Android and iOS respectively. Pulse can be downloaded for free.
You can use the app to easily view your courses, course items, upcoming activities and your notifications on your mobile phone or tablet.
If you don't want to use Pulse, you can open the Brightspace website on your mobile device. The website has a 'responsive' design and works well in a mobile webbrowser.
Want to know how the Pulse app works? Read this article: How do I use the Pulse app?