You have to provide them with information. They need specifics about what you need to do, who you want to talk with - as specific as possible-- what you will talk to them about (is it sensitive?) and how you want to recruit them.
You want to ask for an appointment because this is a vulnerable population and you need advice on how to do it. Or if you even would be allowed to.
My dissertation topic is "Homelessness and its Long-Term Impact on the Emotions and Personality of Individuals".
Sample Solution