Since the create a table partitioning syntax is hard to keep in mind, we'd better use GUI tools to facilitate us to create. Here we introduce the way to create a new partitioned table by SQL developer.
Right click on Tables, it shows a function menu.

SQL Developer - Create a New Table
We enable "Advanced" option.

SQL Developer - Create Table Builder - Click Advanced
Add some columns.

SQL Developer - Create Table Builder - Column
We partition the table by range.

SQL Developer - Create Table Builder - Partition by Range
Select the partition key.

SQL Developer - Create Table Builder - Select Partition Key
Click on + sign to add a new partition.

SQL Developer - Create Table Builder - Add a Partition
Add the first partition segment with values less than TO_DATE('2000-01-01 00:00:00', 'YYYY-MM-DD HH24:MI:SS').

SQL Developer - Create Table Builder - First Partition
The rest of rows go to the second partition segment, so we choose MAXVALUE.

SQL Developer - Create Table Builder - MAXVALUE Partition
We review DDL for making sure that everything is ready.

SQL Developer - Create Table Builder - DDL
Then click OK to confirm.
After we have created the new partitioned table, we can try to load some data.
SQL> insert into hr.sales select * from sh.sales;
918843 rows created.
SQL> commit;
Commit complete.
We made it.