Usually, bloggers make money by putting advertisement banners like Google Ads on their blog site. Everytime a visitor clicks on those ads, you will get a certain amount of money... a few cents most of the time. You are not allowed to tell people to click on the ads because it's against the policies of most online advertisement providers. You just have to hope that some of your visitors will be interested and click the ads. With that being said, you will need at least thousands and thousands of visitors to make some bucks because not everyone will click on ads. Only a small percentage will click.
The bottom line is: your blog site needs to be popular enough if you want to make enough money. Otherwise, a fast food job at McDonald's is always a better way to make cash if the blogging idea isn't working out. Blogging should be a side-job, not your main job unless you become successful with it. When you have accomplished that, then it can become your main source of income.