Open the sidebar, click on Training Assignment and choose Assignment.

Enter the name of the course in the search bar. The results are shown.

Select the required course by clicking on the circle under Select, for the required course.

Now click on Enroll Groups, a grey box in the upper right corner of the screen. The Course Assignment - Enroll Groups screen opens.

Enter the name of the group in the search bar. The results are shown.

Select the group by checking the box, under Select, before the group name. If the box is already checked, it means the group has already been assigned to the course.

Using steps 5 and 6, you can select multiple groups.

After selecting the groups, click on Confirm, a blue box in the bottom right corner of the screen, to assign them to the selected course.