how can i earn in this social media?

Write a good article, with some nice pictures, and if people upvote it you get money for it 7 days after you posted the article. If you're completely new you'll probably have to gain a following first so that there are more people who actually stumble upon the things you write. So read other people's articles, upvote those you like and write comments, engage with the community. You can even make money for upvoting and commenting, but not as much. But it will help you gain followers.

By default you will receive 50% of the money in "Steem Dollars", which you can instantly convert to Bitcoin or Euro/Dollars/Whatever on an exchange like Bittrex.com. The other half will be in "Steem Power", which gives your upvotes more power (so the person you upvote receives more money, and you get more money for upvoting). You can convert that to "Steem" which you can also sell on the exchange for Bitcoin, Euro, etc. But you can't do it instantly. You have to "power down" for that. That is a process where you get 1/12 of the money every week for 12 weeks. But if you want to earn more on Steem, it's better to hold on to it.