Hi Kalyan,
Is not legal to "share" WAS :-)
You can download a trial from here
http://www.ibm.com/developerworks/downloads/ws/wasnetwork/index.html
if you have support you can download from your passport advantage.
Here online repositories to download using your account
http://www.ibm.com/support/knowledgecenter/SSAW57_8.5.5/com.ibm.websphere.installation.nd.doc/ae/cins_repositories.html?cp=SSAW57_8.5.5%2F1-5-0-2-0
or if you want WAS 8.5.5 version and you have WAS 8.5 you only need to install latest fixpack or from fixpack 8.5.0.3 (8.5.5)
8.5.5.9: WebSphere Application Server V8.5.5 Fix Pack 9
http://www-01.ibm.com/support/docview.wss?uid=swg24041819
Hope this helps. Tell us if you need more support
Regards