There are various ways to earn Bitcoin.
1. You can exchange your fiat money to get some bitcoin.
2. You can sell your services, whatever you are good at, and get paid in Bitcoin. (You'll have to finalize this with the client before starting work.)
3. You can earn other alt-coins and convert it into Bitcoin.

I will elaborate the point 3 further. It's not easy to earn free BTC currently but there are some alt-coins that you can earn by doing some work. For example, you can earn STEEM and SBD coins by blogging on steemit dot com website. You can earn SOL coins by creating cards on sola dot ai site. And so on. Find such sites and earn coins from there. Transfer those coins to supporting exchange and sell it to earn Bitcoin. By far, this 3rd option has worked pretty well for me.