By telling them the things that happens to you when you are invesying in bitcoin. And you can also use the internet to show them how
If the one whom you are trying to convince is little educated person and he knows something related to crypto currency, then it will be very much easy thing for you to convince that person for investing his money into any of the crypto currency by making him more and more aware regarding crypto currencies and by telling him all the advantages which are there and which they can enjoy after investing into it.