You can earn money several way through Writing Good Quality content on HubPages:
1) Become a Goodgle Adsense affiliate - write some good quality content, then apply to Google.
2) Amazon Affiliate - apply to Amazon to earn money through placing their product on your hubs
3) Ebay - Apply to Ebay
4) HubPages Ad Program
First thing, join HubPages and Write Quality Original content - then you can apply to the Affiliate Programs.
Also, check out the HubPages Tutorial.
Thanks for the question, hope I have helped!