The portal will be empty until you have records in contacts where the value in Contacts::FIRM_ID is identical to the value in Firm::Firm_ID of your current record on your layout.
Did you enable "allow creation of records via this relationship" for Contacts::FIRM_ID in this relationship?
If so, you can create a new records in Contacts by entering data into a field in the portal row and it will be automatically linked to the current record on your layout. This is just one of several ways to manage the process of getting matching values into your match fields.
Thanks for responding. Can you please elaborate on your first statement - how can I make sure that the value in Contacts::FIRM_ID is the same as Firm::Firm_ID?
I do have the option to create records selected (see image 4).
In terms of creating new contacts I have also done this (see image 5). I am still not able to understand for instance from image 5 I have Contact names RTY and UIO which I want to be related to Firm QWE as per image 1.
I thought that I spelled that out in my first response. If you enter data into the blank "add row" of your portal, FileMaker will create a new record in Contacts and copy the value of FIRM_ID from the current FIRM record into this new record--creating a related contact record.
The two FIRM_ID fields are data fields in your database. Firm::FIrm_ID should be defined to auto-enter a serial number. To link an existing Contact record to an existing Firm record, edit the Contacts::Firm_ID field to give it exactly the same value as that found in the FIRM_ID field of the Firm record to which you wish to link it.
If you have a FIRM named "Acme Consulting" with a FIRM_ID value of 234 and you want to link a contact named "Jim Smith" to that Firm, enter the value 234 into the FIRM_ID field of the "Jim Smith" record. This happens automatically when you use a portal to create your new contacts. If you want to use the contacts layout to link records to firms, you can put the Contacts::Firm_ID field on your contacts layout and format it to use a value list of FIRM_ID values along with the associated Firm names.