Three ways I can think of:
1) Microtasker
You do tasks and get paid for completing them. Usually they have a low payout, that you may not even be able to refund your internet costs (unless you have unlimited internet access).
2) Specialist worker
Offer your skills to others and get paid for taking on requests. Sites like Fiverr and Upwork can give you a good amount of money if you play your cards right, but you need to be able to advertise yourself, otherwise, your gigs will get lost amongst the others.
3) Personal projects
Then there are sites where you can do whatever you want, and others can donate money to you. You do what you love, and others love watching you do it. Patreon and Twitch are two of such sites. Problem again: You need to stand out and advertise.
With 2 and 3 you can actually make some good money, even get rich with 3. But keep in mind that for 2, your pay depends on the people that want to hire you. One month there's 50 customers, the next month nobody. And for 3 it's wishful thinking and never stopping, because it'll take a long time before you can turn it into a job.
Make sure that you keep it at a side job, your main job should always take priority.