Follow the steps below if you're talking about Android cellphones that have the Play Store application. Go to your home screen and choose it. Then go to 'Apps' > Settings'> 'General' > 'Security' (if it exists). Unknown Sources should be checked. Then go to this Web page and download the most recent APK. Then, either open any file manager, such as X-Plore File Manager, and go to the location of the downloaded file and tap on it, or pull down your notification panel and press on the downloaded file to install it. This will start the installation process.
You can no longer download XAP files from the Microsoft Store Web page for Windows Phones. As a result, you'll require Microsoft Store. The most recent XAP files are all from 2015, thus even if you install them, WhatsApp will not operate.
