To grade assignments, from HOME, find the class you want to grade and click on it.
Then, find the assignment you want to grade and click on the "Submissions" in the top right corner.
Grade them INDIVIDUALLY by clicking on the name of the student.
This will display the work, and the place where you put the grade, and allow you to make any comments. Put the student score in the BLUE circle, and the amount of points it is out of in the Red circle, and any comments below that.
If you have an assignment where you want to give ALL the students who turned it in ONE Grade, like for completing the assignment or something, click the "Student Name" box just below the "Turned IN" and above all the classes and names on the left side of the screen, it will bring up this. Do your grades the same way: