If the Issues feature has been activated in a project, an assessor will be able to raise an issue in two ways:
Go to Project > Communication > Issues > Create
Via the answer sheet itself (scroll to the bottom of the answer sheet to add your issue).
Depending on the project configuration, you may have the option to make your Issues:
Private (only visible by the person who raised it and Project Manager/Support)
or Public (visible by all of the project team).