The Listownr Refcard (available via GET) indicates:

List management functions
-------------------------
Commands that support the QUIET keyword are marked (*)

ADD          listname user <full_name>         Add a user to one of your lists,
                                               or update his name
             listname DD=ddname                -> Add multiple users, one
                                                  address/name pair per line

i.e.,

ADD listname DD=INLINE
//INLINE DD *
userid1@host1 firstname lastname
userid2@host2 firstname lastname
/*

--  co-owner:   INFOSYS, TQM-L, CPARK-L, ERAPPA-L, JANITORS, LDBASE-L, et -L
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