If you would like to add an assignment for your students in Moodle, you can do the following:
1. Turn editing on:
2. Select Add an activity or resource near the section where you would like the activity to appear:
3. Once you open the activity chooser menu, you can select Assignment from the top of the list, followed by Add:
4. You will then be prompted to configure additional settings for the Assignment.
Here is a video overview of the Assignment: