Open the .agf and the .dbf (open the .agf first). Open .dbf as unlinked to compare the values in the .dbf file with the _ID column of the .agf. The column with the same values is the column you will use to link the table with the geofile.
-Click on the Define Columns icon or go to Table | Define Columns and select the layer you want to link.
-Click on Links to Geo. The layer to choose is the .agf and the Key Column is the column from the .dbf that has the same values as the _ID column of the .agf.
After clicking on Define Column, if you do not see the layer you want to link in the selection window, it is possible that the table you want is already linked to another geofile. You will have to unlink the table before you can use it with another geofile.
Note: Only one .dbf can be linked to the .agf at a time in a one-to-one relationship.