As noted, you need an active phone number in order to install and set up WhatsApp. If your tablet has a SIM card slot, even better, but if it doesn’t, there’s still nothing to worry about. First, you’ll need to download and install the latest WhatsApp APK for Android on your tablet. To do this, visit the APK Mirror and get the latest version on your device.
Once it’s there, tap on it to install, just like you’d do with any other application. You’ll be greeted with a very familiar window asking you to accept the terms. Tap “Agree and continue” and in case another window pops up telling you that WhatsApp for Android tablets is not supported, don’t mind it, instead, hit OK.