To add curricula to or remove curricula from a class, go to the class Admin page and click the green Edit button.
Click in the Curricula box, begin typing the title of the curriculum (or scroll through the options in the drop-down menu) and click the curriculum you'd like to add. You can add as many curricula as you'd like. If you wish to remove any, simply click on the little cross (x) at the end of the curriculum name.
When you're finished, click on the green Save button, and you'll now be able to create and assign tasks from the new curriculum.