Transfer from where ? I'll assume you mean you receive some files and want to make them accessible to the database.

For me, I'l would look at external tables (although sqlldr will work just fine as well) - you get just more flexibility with external tables.

Anyway, here is the process:

1) place csv files in a location where they are accessible by the database, ie, either on the database server itself or on a file share that can be seen from the server

2) perform 'truncate table' on the target tables, or use the TRUNCATE keyword in your sqlldr control file

3) load the tables with

insert /*+ append*/ into target_table
select * From external_table

or run your sqlldr load process.

Plenty of examples of both all over AskTOM.