To change your own login password, use the following command:
To change passwords for other accounts in your server, use this command:
For both commands, you should be seeing an output like this:
Enter new UNIX password: Retype new UNIX password: passwd: password updated successfully
Make sure not to have your password too simple, and recommended to mix in at least 1 upper case alphabet, 1 lower case alphabet, punctuation marks and special letters to lower possibilities of accounts being compromised.