This guide it's valid for the Linux packages only. On Windows it's strongly discouraged to install apps. If you need to install an app and have Windows, contact us for a package changing.
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Go in "Apps" > "All apps"
(Click on the images to zoom)
Search "Magento", then click on "Install".
Fill the spaces as in the example (with your data) and click on "Install".
If all went good, you should see a window like this.