Hello welcome to the forum! There are many ways to earn bitcoin. This question is often asked, you can look at the recent posts in the beginner section  

Here is a very short summary.

1. long term buy and hold on bitcoin, wait for it to appreciate in value
2. trading of alt coins, be very astute about trading and purchase coins when they are undervalued and sell them when they are expensive
3. signature campaigns - here you are paid usually in alt coins, for this you need to be at least a junior member on this forum for most campaigns
4. bounty campaigns - here you are paid to promote a coin with Twitter, Facebook, social media articles, it depends what they need, learn about these programs here https://bitcointalk.org/index.php?board=238.0

best of luck