How to change your shell account password
From SHellium Wiki
Once you're logged into your shell account via ssh, type passwd
username:~$ passwd
You should then see:
Changing password for username user (current) UNIX password:
Enter your current password.
Assuming that you entered the correct password, you will then be prompted for a new password twice.
New UNIX password: Retype new UNIX password:
If both fields match, passwd will change the user password and exit sucessfully:
passwd: password updated successfully