You should not convince them directly because many people who are less knowledgeable about Bitcoin will not be easy. First of all, you have to show some proof of other people's income as well as your own income. Then show them even the Bitcoin price to influence them a bit more about Bitcoin's legitimacy. After that you have to show them the Bitcoin seller to make them understand and how much potential they have. You should be as often as possible with them, but if you emotionally tell them that they can make a lot of money, chances are they will find it as Ponzi. Show them the reality, if they are a little smart they will know the rest. To become a successful person.