To convert your datasource into a format that will allow you to edit it or
add recipients, use it as the datasource for a directory type mailmerge with
the mergefields in the cells of a one row table in that document.  When you
execute that merge to a new document, that document will contain a table
with one row for each record in the datasource.  If you insert a row at the
top of that table and enter the field names into that row, and then save
that document, you can use it as a datasource.

Another thing that you might want to do is to select Toolbars from the View
menu and check the mailmerge item. That will cause the mailmerge toolbar to
be displayed.  Now, from the Tools menu, select Customize and on the
Commands tab of the Customize dialog, select the All Commands category and
scroll down through the list of commands until you locate the Mail Merge
Helper item.  Left click on that and drag it onto the Mailmerge Toolbar.
When you click on that button, it will display the Mail Merge Helper that
was used in versions of Word before XP.  In section 2 of the Mail Merge
Helper dialog, you will be able to access your datasource and edit it.