In order to add/view/modify an user, you need to follow the path System Admin -> General Rules -> Security -> User.
Fill in the Name and Search Key fields.
In the Password field, enter the user's password, which must be made up of the following elements:
at least one capital letter;
at least one digit;
at least one special non-alpha-numerical character.
The system will not allow you to save the record if the password does not meet the conditions described above.