Hi SavageJim,
You need to create an association between the tables before you can use the 'Add a Linked Field' option. So for instance, you have Table A and Table B, you then have to figure out something unique that links the two tables. For example, you can add a dropdown field to Table A, 'Full Name' that contains unique values. You now have created a relationship. At this point you can add a linked field. The following post contains another example, to help you understand how linked field works: http://www.methodintegration.com/cs/forums/p/381/1191.aspx#1191