You can also upgrade iCloud storage on Mac, iPhone/iPad. Click here for details.
Mac - iCloud Storage Upgrade (Purchase) iPhone/iPad - iCloud Storage Upgrade (Purchase)
To use iCloud on Windows, you need to install “iCloud Control Panel”. First, let’s start the installation by referring to here.
How to use iCloud on Windows
Windows - Upgrade (Purchase) iCloud Storage
Windows8 - show/hide system icons in notification area
In this way the capacity is increased to 20 GB.
