Edit the relationship to the Table Occurrence for the portal in the Relationships Graph (File>Manage>Database…) and check "Allow creation of records in this table via this relationship". This will provide a blank row at the bottom of the existing rows in the portal. Use this to enter new records one at a time.
I have done this but perhaps there's some detail that I'm missing. I'll admit I don't have the best understanding of the way relationships work. In each table (Organization and Representative) I've added Representative ID. I connected these two fields to create a relationship and selected "allow creation..." Still I'm unable to edit more than one record through the portal.
Thank you for helping
You'll need to check out the details.
"Allow Creation of records via this relationship" has to be set for the portal's table (table occurrence actually). It's possible you selected this for the wrong table.
If you've created multiple table occurrences that refer to the same data source table, your portal has to refer to the same table occurrence in its "Show records from" box (portal setup) as you've used to set up this "allow creation..." option.
Just two possible areas where you may have gone wrong.
Also, if you've place a portal to Representative on your organization layout, the RepresentativeID field should be an auto-entered serial number in Organization, but only a number field in Representative. If you've done the opposite and place a portal to Organization on a Representative layout, you'd do the opposite.