1-befor start thinking about adsense...you need information about creating blogs or websites. 2-and you have to learn about Seo. 3-you have to find a the best topic for your site.(Read adsense TOS carfuly befor start a website) then start your website and wait tell you get more then 100 visitor/day. 4-then apply on google adsense( read about it on internet) 5-wait about 4 mounths after applying to start earn money.Read adsense TOS carfuly) 6-don't try cheat adsnese..or you will get banned.
At first needed your own blog, website or revenue sharing article site, revenue sharing answaring site any one then post some unice articale posting then apply adsense i think google approve your application thats it you enjoy earning.
You will earn based on the number of people clicking the ads in your site. It's called payper click. I'm sure you will find more about that on their terms and agreement.
If you already have a website adsence, you need to do optimization. One key to optimization is "disguised advertising so as not to look like ads"
Simply create an adsense account , create an ad, then post your ad online somewhere and wait for earnings to show.