Hello Gaurav,
is the VPN SSL going to be terminated on the C3825 on in another device like an ASA?
for VPN SSL on C3825 you can read the config chapter from 12.4T security
http://www.cisco.com/en/US/docs/ios/sec_secure_connectivity/configuration/guide/sec_ssl_vpn_ps6441_TSD_Products_Configuration_Guide_Chapter.html
take in account possible licensing aspects:
Licensing
Starting from Cisco IOS Release 15.0(1)M, the SSL VPN gateway is a seat-counted licensing feature on the Cisco 880, Cisco 890, Cisco 1900, Cisco 2900, and Cisco 3900 platforms. A license count is associated with each counted license and the count indicates the instances of the feature available for use in the system. In the case of SSL VPN, a seat refers to the maximum number of sessions allowed at a time.
You can get the license at http://www.cisco.com/go/license.
see also the section
Configuring the SSL VPN Gateway to Distribute CSD and Cisco AnyConnect VPN Client Package Files
Hope to help
Giuseppe