Answer:
My first question here is "Why would you want to?"
A person's spiritual path is their own personal business. Converting someone else is not just unadvisable but unethical.
Wicca is not a cult nor is it wicked, harmful or sinful. Most practitioners of Wicca and other pagan paths are kind, caring, ethical people… It is unrealistic to make a blanket statement about All practitioners. As with any group, there are those who are do not live up to the ideals.
I recommend you look carefully at the person you think you need to convert. If they are living a good, ethical life, it is not up to you, or anyone other than that person to force a change of spiritual path.
To quote Siana Lynn Darrow… "If by worshiping a god or gods one become a person of morality and kindness, then the name by which you call that god or gods becomes of no consequence whatsoever."