Open Manage | Database | Relationships.
Click the button in the bottom far left corner of the window to create a new table occurrence.
Select "Add FileMaker Data Source" from the drop down in the dialog that appears when you click this window.
Use the dialog that then opens to find your copy of the contacts starter solution and select it.
Then select the desired data source table from the list of such from that file.
You now have a table occurrence that refers to a table in the Contacts starter solution and you can reference it in other parts of your inventory database just as though this field was defined in the inventory file. This process also creates an entry in Manage | External Data Sources that refers to the file. The one Caveate is that this reference refers to a specific file located in a specific folder on your computer. If you move the contacts database or change it's name, FileMaker will be unable to find and open this file when your inventory file references data in this table.
Thanks for your reply, PhilModJunk! Where, exactly, is the new table occurrence button? I've been looking through all of the various windows, but I can't find it. Thank you!
Open Manage | Database | Relationships from the FILE menu.
Click the button in the bottom far left corner of the Manage Database window to create a new table occurrence.
It shows up in my relationships tab, and I am able to create a Relationship, but it doesn't show up on my Tables tab, and the field I'm trying to get to populate comes back filled with <Unrelated Table>. I'm sure it's something simple that I'm not doing. Thank you for your help and your patience!
It will not appear in the tables tab nor does it need to. It's not a table that you've defined in the local file and those are the only ones that appear on the tables tab.
If you are getting <Unrelated Table>, it would appear that you have not linked your new table occurrence to the table occurrence of the layout where you attempted to add this field.