There are different ways to make money online, it all depends on you and your level of commitment.
Freelancing: You can make money by offering freelance services to other people, these services range from writing, copy writing, virtual assistant, consultancy, web development, animation among others, to get started you need to open an account in one of the freelancing marketplaces, popular ones are Fiverr, Upwork, People Per Hour etc.
You also need to invest time and learn one of the skills I listed, because your competency will help you to keep clients and will also help in getting referral.
Blogging: You can also look into blogging, but before you get started with this you have to research and find out a niche that has higher audience and lower contents, don't blog about what you like, because nobody cares about you or what you love, people care about what's in it for them, so focus on providing contents that people are already looking for, if not, your blog will just be another page on the internet.
Digital Marketing: Digital marketing is also another way of making money online which involves offering marketing services to business owners through digital means I.e social media, blogs etc