First begin by going to http://www.google.com/adsense, sign in with the email and password you have registered. It will bring you to the Report page. On the main report page it will tell you a total amount owed to you. If you would like a more indepth report click the Advance Report tab and insert a start and end date. This will bring up a list of how many impressions your site has as well as a eCPM, CTR and number of clicks on adsense links and totals earnings. To make it even nicer its sorted day to day to show when your busiest period is or if you know you've made any changes you can see if its improved or hurt report.
Hope this is helpful