Hi kabeer.ece07,
If to have a smartnet contract I recommend you to open a case with TAC.
Just go to cisco.com ---> support -- > open or view cases and open a new case , or call the customer service :
1 800 553 2447
1 408 526 7209
Anyway answering your question:
In order to upgrade your ASA you have to download the new version from Cisco.com
**Go to Cisco.com ---> support --- Downloads and search the version you need .
After that you need to transfer the software to the ASA , It could be done from a TFTP server or via ASDM.
Once you have the file into the ASA go to the config mode and type the following commands :
Boot system flash:name of the image
Write memory
Reboot
After reboot you can check the version with the "Show version" command
Also check this link:
http://www.techrepublic.com/blog/data-center/five-steps-to-upgrading-the-software-on-a-cisco-asa-5510/
Hope this help.