External Tables binding to Access?

I only find information connecting Oracle external tables to data files. But I dont want to transfer data to files instead I want directly transfer data to oracle from Access. I do not know how to change the syntax of the below External table binding

CREATE TABLE city_populations_ext (

   city_name VARCHAR(9),
   pop_1990 NUMBER,
   pop_2000 NUMBER
)

ORGANIZATION EXTERNAL (
   TYPE oracle_loader
   DEFAULT DIRECTORY census_data
   ACCESS PARAMETERS (

      RECORDS FIXED 20
      LOGFILE census_data:
        'city_populations.log'
      BADFILE census_data:
        'city_populations.bad'
      FIELDS
      MISSING FIELD VALUES ARE NULL (
          city_name (1:10) CHAR(9),
          pop_1990  (11:15) INTEGER 
        EXTERNAL(4),
          POP_2000  (16:20) INTEGER 
        EXTERNAL(4)
          )