You can install your software by:
- Opening the QGIS website in a browser: http://www.qgis.org/en/site/
- Click on the “Download Now” button (version 2.8.1)
- Download the Installer for your laptop (for Windows, ensure you select the correct bit size.)
If you are not sure which bit size your laptop is, go to “Start > Control Panel > System”. The details should be under System type (32 or 64 bit).
QGIS allows you to download installers for Windows, Mac OS X, Linux, BSD and Android.