If you can't make head nor tail of it, try this one :
SQL> create table tbl_long (id number, text long);
Table created.
SQL> create table tbl_clob (id number, text clob);
Table created.
SQL> insert into tbl_clob select object_id, object_name from all_objects;
22074 rows created.
SQL> select * from tbl_clob where rownum<=5;
ID TEXT
----------------------------------------------------------------
18159 /1001a851_ConstantDefImpl
7781 /1005bd30_LnkdConstant
4841 /10076b23_OraCustomDatumClosur
17099 /10297c91_SAXAttrList
17712 /10322588_HandlerRegistryHelpe
SQL> commit;
Commit complete.
SQL>
SQL> declare
2 my_char varchar2(32000);
3 begin
4 for x in (select id, text from tbl_clob) loop
5 my_char := dbms_lob.substr(x.text, 32767, 1);
6 insert into tbl_long (id, text) values (x.id, my_char);
7 end loop;
8 end;
9 /
PL/SQL procedure successfully completed.
SQL>
SQL> select * from tbl_long where rownum<=5;