To create a link with your phone number, use this link: https://wa.me/number and replace the word "number" with your full phone number in international format. Do not include parentheses or dashes.
You can also create a link with a predetermined message which will automatically appear as an option for the customer. That way your clients can save time when messaging you.
Replace "number" with your full WhatsApp phone number, and replace "message" with your predermined message. Use %20 between words to include a space.
So far, we have told you how to create the link manually. To do it automatically with a tool and simplify the process, we recommend our WhatsApp link generator that you can use for free.
You can also use this or this other generator to create a QR Code.