Hi Sanjeev,
I did the same thing using ASDM. Steps are mentioned below:
Go to configuration > firewall > service policy rules
click ADD in the popup menu select the "interface" radio button and select the interface you wish to apply the rate limit to.
Step 1:give it a name, and click next
Step 2:select the "create new traffic class" radio button and give that a name also
Step 3:select the "any traffic" check box
click next
Step 4:select the QoS tab
Step 5:check the "enable policing" checkbox
fill out your rate limit options and apply the policy on the desired interfaces.
Regards,
Anim Saxena
Community Manager