On your profile, there will be a settings portion. In settings, you will be able to edit your advertising preferences. Here you are able to opt-out from interest based advertisements if you would like to.
Blocking interest based advertisements does not opt you out of being served advertisements. Instead, you will receive general advertisements that do not necessarily have to do with your interests, past searches, and purchases. In concerns of your privacy, you need to grant us permission to serve interest based ads.