How to add partitions to the existing table in PostgreSQL

How to add partitions to the existing table in PostgreSQL

for ex, below is my table definition:

CREATE TABLE ot.employee
(
empno smallint NOT NULL,
ename character varying(20),
job character varying(20),
deptno smallint
)

Now I would like to add partition to deptno column

I don't see any alter table command to add the partition to the existing
table.

Please help me on this.

Thank you
Naveen