Here it is with an example file and the four steps:
1. Go to the import player action in the upper right of the Free Agent screen and select the historical_database.odb file.
2. Choose any other options you like (for example I always tag the import to show me the real life stats of the year I'm importing - but all this is up to you, the rating options, the adjustment levels, etc.)
3. Clear the name and year as you are not using them, you are instead going to select "Click here to select file". You then have to navigate to where ever the .txt file is. I had mine in My Documents folder so that's where I had to navigate to. Doesn't matter where it is - just have to navigate to it. Note: it has to be a plain text .txt file in the format I attached. I saved this one in "Notepad". I didn't put a team after each name but I could have based on whatever abbreviation your fictional teams have for themselves. Absent a team, they just become free agents which is how I have it.
That example formatted Notepad txt file is at the bottom of this file for download. Add as many names as you like with or without a team to send the player to.
5. They should import...