Select 'classroom' on the classroom tile.
Select Create Lesson Plan.
Make sure the 'Assignment' tab is open. Select 'add: +'.
Select a chapter using the < and > buttons.
Optionally, you may select a single problem type.
Write a description. Then select either 'Assign entire chapter' or 'Assign only this problem type'.
You should now see your newly created assignment on your assignment list.