The Download Now link directs you to the Windows Store, where you can continue the download process. You must have an active Microsoft account to download the application. This download may not be available in some countries.

WhatsApp Messenger is a FREE messaging app available for Windows Phone and other smartphones. WhatsApp uses your phone's Internet connection (4G/3G/2G/EDGE or Wi-Fi, as available) to let you message and call friends and family.
Switch from SMS to WhatsApp to send and receive messages, calls, photos, videos, documents, and Voice Messages. WHY USE WHATSAPP: NO FEES: WhatsApp uses your phone's Internet connection (4G/3G/2G/EDGE or Wi-Fi, as available) to let you message and call friends and family, so you don't have to pay for every message or call. There are no subscription fees to use WhatsApp. MULTIMEDIA: Send and receive photos, videos, documents, and Voice Messages. FREE CALLS: Call your friends and family for free with WhatsApp Calling, even if they're in another country. WhatsApp calls use your phone's Internet connection rather than your cellular plan's voice minutes. Available on Windows Phone 8+. (Note: Data charges may apply. Contact your provider for details. Also, you can't access 911 and other emergency service numbers through WhatsApp). GROUP CHAT: Enjoy group chats with your contacts so you can easily stay in touch with your friends or family. WHATSAPP WEB: You can also send and receive WhatsApp messages right from your computer's browser. Available on Windows Phone 8+. NO INTERNATIONAL CHARGES: There's no extra charge to send WhatsApp messages internationally. Chat with your friends around the world and avoid international SMS charges. SAY NO TO USERNAMES AND PINS: Why bother having to remember yet another username or PIN? WhatsApp works with your phone number, just like SMS, and integrates seamlessly with your phone's existing address book. ALWAYS LOGGED IN: With WhatsApp, you're always logged in so you don't miss messages. No more confusion about whether you're logged in or logged out. QUICKLY CONNECT WITH YOUR CONTACTS: Your address book is used to quickly and easily connect you with your contacts who have WhatsApp so there's no need to add hard-to-remember usernames. OFFLINE MESSAGES: Even if you miss your notifications or turn off your phone, WhatsApp will save your recent messages until the next time you use the app. AND MUCH MORE: Share your location, exchange contacts, set custom wallpapers and notification sounds, email chat history, broadcast messages to multiple contacts at once, and more. Data charges may apply. Contact your provider for details. We're always excited to hear from you. If you have any feedback, questions, or concerns, please email us at: wp-support@whatsapp.com or follow us on twitter: http://twitter.com/WhatsApp @WhatsApp.