Vijay-- I feel your installation is not done properly also, while in the installation process what all adapters did you select to install. Also, please share installation logs for more information for us to better suggest.
A) Shutdown IS.
B) Take a backup of jdbc.cnf from /packages/WmDB/config
C) Delete this file and restart IS
Please note this will help to get around the NullPointer Exception and the WmDB link will be available under the Adapters menu on IS, but you may need to create the wmdb connections/aliases.