Welcome to FileMaker and to the FM community.
A good training resource to get you started is here: Database Skills, FileMaker Pro Training | FileMaker
With your portal - you cannot simply copy and paste from another database. In your layout - double click the portal which should bring up the Portal Setup window. The first part of that window says "Show related records from: " and has a dropdown list. You can then select a related Table Occurrence (TO) in your database that you want to show related records from. If you cannot find the correct TO in the dropdown list, scroll to the bottom of the dropdown list and there should be an option to Manage Database. Select that to set up a TO for the related records.
Once you have the portal looking at the correct TO, then you will also need to make sure that each of the fields in your portal are based on the same TO that the portal is based on (or other related TO from further down the chain of relationships).
Can you attach two pics:
1. the layout where you have the portal.
2. the relationship graph.
This will help us see what is awry.