Why do you think there is something special required to earn cryptocurrency? Cryptocurrency, Bitcoin, is currency...it's money. You can earn it by doing anything in this world that someone will pay you money for.

What do you do for a living? How do you pay for your food, home, clothes, etc? Whatever this work is that you do currently, do it more - for more people, more hours a day, or do it better so you can earn more money or charge a higher rate.

Then, ask your employer or customers to pay you in Bitcoin. If they refuse, no worries, take the money they pay you with and buy Bitcoin.

It's that simple.