Homework Check is a separate course screen: a list of student answers with filters and a pass/fail rating.
To check homework, open a course and select "Check Homework" in the bottom navigation (or "Unchecked Homework" from the teacher's lounge). Filter the answers—"New" is shown by default—open the desired branch and mark them as "Pass," "Pass with Comment," or "Fail" (if failing, specify the reason). You can immediately notify the student via email. After saving, the system will automatically suggest the next unchecked answer.
Each answer is checked individually in its own thread—there's no mass checking of checkboxes in the general list yet. And if auto-credit is enabled, an answer can be credited immediately, without the teacher's intervention.