Just like Bubblious said! We earn them by answering and asking questions ;) Don't worry if you don't have followers your first couple of days. Just be sure to answer/ask questions nicely and people will follow you! :-)
Some users have a 'follow back' policy, where if you follow them they'll follow you back. But you can also gain followers by asking good questions, giving helpful and constructive answers, and getting to know people by having a conversation in the Comments section under answers. :) Just make sure you're familiar with the Community Guidelines:
Hi M! It takes time. Ask good questions, give good helpful answers. Be an active member, get to " know" people.The followers will come if they like what you have to say. We are not like Facebook, you have to earn followers here. Don't worry about it, just have fun!