WhatsApp's Click to Chat feature allows your visitors to message you with just one click made from your landing page.
First, you need to add a button element or an image element on your page.
You can customize it and place it as you wish. Now you need to select Click Event, then Outside URL and enter
https://wa.me/<number> where the
<number> is your full phone number in international format.
Omit any zeroes, brackets or other symbols when adding the phone number in international format. If your phone number is +001-(555)1234567, use
https://wa.me/15551234567 not https://wa.me/+001-(555)1234567
Keep in mind that you must have an active account on WhatsApp for the number you are using.
To create a link with a pre-filled message that will automatically appear in the text field of a chat, use
whatsappphonenumber is your full phone number in international format and
URL-encodedtext is the URL-encoded pre-filled message.