Follow the following steps to create groups and to assign courses to groups.
Login to your LMS domain
Navigate to List Group under Accounts and settings.
Click on Add Group.
Enter Group name and Group description and click on Save.
Click on Add users in the option column.
Select the users you need to add in the group.
Navigate to Course.
Click on more on the course that you need to add to the group and select Assign user group.
Select the user group to assign the course and click on save.