You need to write an article by clicking on the 'Write' option on the top of the page. You can also click on 'Help' and look for your questions about writing an article and earning money. The HubPages Help website contains all the frequently asked questions.
You have to then make a Google Adsense account if you do not have one. If you have a Google Adsense account, you can link your account with that one and enroll yourself in the HP Earnings program. As and when you get views, you'll start getting paid.