You cannot (and do not want to, believe me) force them. They must hear the call of the camino for themselves. But you can make sure the message is delivered: youtube videos, blogs, books and memoirs. However, you must do this in the spirit of, "This may not be for you. You will have to decide for yourself. But I would be glad of your companionship."
Even if your friend consents to go, there is no guarantee of traveling bliss. That depends on compatibility of rising, eating, and sleeping hours; traveling styles; etc etc.