In order to add an assessment to an existing assessment plan assigned to a batch, you can:
1. Click on "Courses"
2. Select "Batches"
4. Once done, click on the "Settings" tab on the top-right corner of your screen.
5. Select "Manage Assessment Plan"
6. Click on "Manage" in the pop-up
7. Select "Add Assessment" here.
8. Choose the "Assessment" from here.
9. Select the students from here.
10. Choose "Start Date".
11. Choose "End Date".
12. Save.
Please note that adding an assessment to a batch will mean changes effecting only for the batch and not the entire course.