From the optimise seating sidebar instead of clicking the 'Optimise seating' sidebar, click the 'Make Groups button'.
After clicking this you can choose how many groups you would like to make and optimise the sliders to your specifications. Then click the 'Make groups' button again to put them into groups.
Students will now be in groups. You can move pupils between groups and even select a whole group if you would like to award multiple points by clicking on the group number.