In order to earn money from Google AdSense, you need to have a website that has been up for around 6 months and you need to have original and quality content that is useful for the visitors. If you have such a website, you can enroll in the AdSense program and start earning money by displaying their ads on your website. When someone clicks on the ads, you make $$$. The key is to bring a lot of targeted traffic to your site. More traffic = More money.
Well, first of all you can start with blogger as its free. Make a blog and put up good content and drive some traffic towards it and then apply for Adsense. If your blog is good they will accept you. And then you can earn via adsense. - Digital -