Flags will be indicated on the class overview but to access them you'll need to go to the Results tab.
Click Attributes and then click the small arrow next to Flags to bring all flags to the top. You can also deselect all attributes except flags. This will make it easier to find the flags.
You can either choose to view flags from the receiver or the giver of the flags by clicking on the submission or reviewers tab.
Click on the students name and the feedback and flag will appear on the right side.