In what two ways do the principles say psychologists could do harm?

The correct statement is that the psychologists can harm the clients by providing wrong or false or misleading information and by not taking the correct, necessary actions.

Psychologist are meant for curing the conditions of the person who are suffering from mental illnesses, trauma and stress, etc.

Psychological harmA psychological harm can be referred to as the harm which is caused due to the faults made by the psychologists during their consultancy with the client. If a psychologist provides misleading or incorrect information during providing consultancy services to their clients may lead to mental damages to the client. In such cases, where the psychologists take the wrong actions or steps which were not meant to be taken for curing the mental illness of their client, may lead to increase in illness causing harms.

Hence, a psychologist can harm the clients by providing wrong or false or misleading information and by not taking the correct, necessary actions.

Learn more about psychological harm here:

link

The two ways are:
- actions done that result in harm 
This happens through a form of direct action such as giving the patient with false medication that worsen the condition of the patient.

-by information not given that result in harm
This happen by indirect action such as supporting patient's delusional thoughts that ended up in them acting on their delusion and hurt themselves.

Ibelieve its c not quite sure.