Trying to add new field to table

[bradp1979]

I'm trying to add a new field to an existing table. The field I am trying to add is in the "Field available in related tables" pane, but when I try to drag and drop, I get the "forbidden" symbol, and when I double click, nothing happens, likewise when I right-click and click on add field to view.

What am I doing wrong?

[CJ_London]

forgive my ignorance, but what is the "Field available in related tables" pane?

[orange]

Have you tried opening the table in design view, and adding the field manually?
Also, as Ajax said --what is the "Field available in related tables" pane?? Haven't heard of that.