For basic information how to start this business, you can go to Google and search for Data Entry Jobs and you can see a lot of websites offering those kind of jobs. But beware of scams. Data entry is the most widely scammed money making in the internet.
To avoid scams, especially for the beginners, you can visit a friend's site that offers free ideas how to avoid scams and how to find legitimate data entry companies. Check his site at http://dataentryjobsforbeginners.blogspot.com