A portal requires that you have at least two Tutorial: What are Table Occurrences? in Manage | Database | Relationships linked in a relationship. You base the layout one one of these table occurrences and the portal on the other. The relationship linking the two occurrences then controls what records, if any, appear in the portal.
How do you want your portal to work? What records should be listed in it? All of them? Some of them with some criteria that controls which appear and which do not?