The procedure to create and import a signed SSL Certificate for the Self-Service Portal Node is exactly the same as the procedure for the Management Server except the Portal uses the portal.keystore instead of webserver.keystore.
The procedure is located in the Installation Guide for the version of Data Insight installed.
The SSL Certificate procedure is listed under the section About post-installation security configuration for Management Server.
Documents can be accessed from SORT:
https://sort.veritas.com/documents