Welcome to hubpages!
There are many ways - all you need is a Google search. In fact, there are quite a good hubs (articles) on Hubpages itself.
If you are good at writing and are a bit of Tech Savvy then you could write of Hubpages and similar sites and earn money from the ads placed on your behalf on your pages.
Similarly, you could write bogs on blogger.com or create your own websites / blogs.
For all these you will need adsense.
Thirdly, you may also use your writing skills to do product reviews, copy writing etc.
Technically speaking you are earning by devoting your time and putting in your skills. Is it not selling? Otherwise how will you earn?