Changing your password can be done through the command line with passwd.
euid123:~$ passwd
Changing password for used euid123.
(current) LDAP Password:
New password:
Retype new password:
passwd: all authentication tokens updated successfully.
New passwords should be slightly complex (meaning digits 0 through 9, punctuation marks, and different cases of letters), otherwise the command will reject it (and if not, it should reject it). Passwords should be at least 6 characters long. If the system requires regular password changes, then it will alert you that it is close to expiring.