PPD would send you an email to set up a phone interview and also send you a list of questions which you shold send them before the phone onterview. After the 1st phone interview if you are selected they have you set up another phone in interview. Post that one if your are selected they have either a face to face interview or Skype interview. After that they let you know if you are selected or not.
Questions are usually scenario based - what did you do when..... you just have to give your experiences. Also they may ask why you want to be a CRA and what interests you to be one.