How to use WhatsApp on your iPad
If you don't already have a WhatsApp account, you'll need to set one up before you can use the messaging app on your iPad. Then open a new tab in a web browser — like Safari or Google Chrome — on your iPad and follow these steps.
1. Go to web.whatsapp.com. The WhatsApp web interface will appear.
2. Open WhatsApp on your iPhone. Tap Settings at the bottom right of your screen to bring up the Settings menu. Tap WhatsApp Web/Desktop.
3. Move your phone in front of your iPad to scan the QR code on the iPad screen. If the QR scan screen doesn't come up automatically, tap Scan QR code.
4. Once the scan is successful, this screen lets you know you've connected another device to WhatsApp.
5. Now you can view and respond to WhatsApp messages on your iPad. Note that this is done through the connection with your phone, so your WhatsApp messages won't live on your iPad.
If you want to log out of WhatsApp on your iPad, you have to log out of all devices and then log back in on your phone.
You can do this by tapping "Log out from all devices" on the Web/Desktop settings screen and then choosing "Log out" from the box that pops up.