Home > Welcome to Moodle > Users, Enrollments, & Moodle Access > Groups of Students (in your Moodle Course) > Manually Add Students to Groups
In the Groups tab, select the group you want to add participants to.
Click the Add/remove users button.
In the Groups tab, select the group you want to add participants to.
Click the Add/remove users button.
You will be taken back to the Groups tab.
Repeat this step as necessary to add students for each Group.