sqldeveloper is only a client tool, so you are NOT importing in sqldeveloper, you are importing in Oracle database.
At the same time you provide no info at all on WHAT you are doing so no one can spot your error.
External table syntax is here
Refer to 'date_format'.
Senior Oracle DBA
Following shall be the steps:
1- Change the corresponding column of table to varchar2 instead of timestamp in Oracle table.
2- Now import the data into the table using SQLDeveloper
3- Add new column in the table of timestamp with time zone type e.g. new_column
4- populate this column using the update statement e.g.
set new_column = to_timestamp_tz(varchar2_column,'yyyy-mm-dd hh24:mi:ss TZR')
5- Now drop the varchar2 column
You need to define the Timestamp format on this step:
With all due respect to the advice to import this date data as a varchar2 'string' - please do NOT do this. Store dates as dates (or timestamps), strings as strings.