The first step would be to establish yourself. Ensure that you have a secure job that not only pays the bills but leaves you with enough money to live your life independently. Second explain your reason for not wanting to get married. Parents don't usually understand the solo culture since it isn't a concept that they were exposed to growing up. Marriage is a must in our society and us being so involved in and influenced by it can't take the road not taken so easily. Parents will also worry about things that society would say about you should you not marry. So the last step is to convince them that what people think of you doesn't matter as long as it isn't the truth. People keep switching from gossips about one person to the next and lies always die down after a while.