How do I change my Oracle user password ?

C:\>sqlplus testuser/Password@//ractest-scan.ractest.local:1521/service

SQL*Plus: Release Production on Fri Aug 31 11:44:13 2018
Copyright (c) 1982, 2014, Oracle.  All rights reserved.

Connected to:
Oracle Database 11g Enterprise Edition Release - 64bit Production
With the Partitioning, Real Application Clusters and Automatic Storage Management options

SQL> password

Changing password for TESTUSER
Old password:
New password:
Retype new password:
Password changed