Hello Jasbir,
If you already have the required signer certificate (You really should contact the admin of the target host or look up information available to you to get the signer certificate, this is the best practice) you can add the certificate by following these steps in the Knowledge Center:
Adding a signer certificate to a keystore
https://www.ibm.com/support/knowledgecenter/SSEQTP_9.0.5/com.ibm.websphere.base.doc/ae/tsec_ssladdsignercert.html
You can use retrieve from port to "steal" the signer from any host that will allow that as long as you know the proper protocol and cipher requirements and port number.
See this article in the Knowledge Center:
Retrieving signers from a remote SSL port
https://www.ibm.com/support/knowledgecenter/SSEQTP_9.0.5/com.ibm.websphere.base.doc/ae/tsec_sslretrievesignersport.html
Also this video that my team made:
https://youtu.be/Bv_l8aipagY
Regards,
Bill Holtzhauser
#Support#SupportMigration#WebSphereApplicationServer(WAS)