Kalyan,
URLs a repositories to configure from Installation Manager (IM) NOT to download directly. And from IM you need to have and ID with software support active.
To download you need to go to passport advantage and authenticated with your customer ID
https://www-01.ibm.com/software/passportadvantage/pao_customer.html
If you are Business Partner (and you have ordered Value Package) you can download from PartnerWorld from Software Catalog section
https://www-356.ibm.com/partnerworld/wps/servlet/ContentHandler/partnerworld-public
Finally (if you NOT have software support nor Value Package) you can download a trial from:
http://www.ibm.com/developerworks/websphere/downloads/
Hope this helps. Tell us if you need more support
Regards