Thanks Victor, But there is something wrong with me.
1 )I downloaded the license key, and replaced the existing sitefinity.lic file under App_Data. Then i browse the site and it shows me a license activation window as attached (trial.png) .
2. Then I tried to activate it using my sitefinity account (firstname.lastname@example.org). Then it shows me another page as attached (online.png).
3. Then I tried manual by uploading my sitefinity.lic file and it shows (manual.png).
Now I reverted back to my old Sitefinity.lic file(it shows trial version). Please help me out quickly as it is very important as site is live.