I got one E-mail stating that I am a DV Lottery winner.

Don't believe that E-mail, because the American Government is still not using the E-Mails to inform the DV lottery winners. The email sender should have got your E-mail address from a public place like forum, pen pal web sites or in some web site where you became as a member to use their facilities and the web site owner or administrators has sold your email address to those crook people. If you look good, it will address you as "Dear winner" as they don't know your name. Also you will find the American Government departments and other office names in the E-mail. But the place they want you to send money is not any of the American Government's addresses. It will be some crook persons address where they want to collect the money for their personal use. Don't answer to that E-mail or don't try to contact them at the given telephone number.

Then how will they notify me if i am a winner?

If you are selected by the computer in the random DV lottery draw, between May and July they will use regular mail to inform you with further instructions and the related non refundable visas fees and diversity visa processing fees.

The address you gave in the entry form will be used to send the DV lottery winning notification mail. If you had shifted from your original address and now living in another address then you must ask someone in the original address to collect any mails coming in your name in that period.
The scam email sender uses the following words to attract your attention. They are dvlottery Americaine and American dream card.
The U.S State Department has some plan to communicate with those people who sent their visa application form as the DV Lottery winners.