Luckly i find a way to do this:
step 1:add the required fields in messaages.properties
C:\DSpace-dspace-4.2\dspace-api\src\main\resources
step 2:Run the following command means rebuild your dspace in cmd
c:\dspace-source/dspace>mvn package.
step 3: Run in cmd the following command
c:\dspace-source/dspace/target/dspace-4.2.build>ant -D dspace/config/config.cfg update
Note: dspace-4.2 is my dspace version and dspace is my installed directory so you need to change it according to your dspace version and installed directory.
step 4:
C:\Dspace\config/dspace.cfg,C:\Dspace\config\spring\api/discovery.xml,C:\Dspace\config\modules/discovery.cfg. also needed to change or add the requied fields Note:Dspace and dspace means installed directory.
step 5:
After making changes in discovery files you need to run the following command to commit that effect otherwise it will not work.
C:\dspace/bin>dspace index-discovery -b
cheer up!