Go to Accounts>Groups, and click on the subgroups link for the Group you need to adjust.
Then, click on the Trainees link next to the subgroup you need to adjust.
This will bring up a list of trainees in that subgroup. If the user has never taken any training assigned through this group, the delete icon will be red and you can simply click Delete to remove them from the group. However, if they have accessed training assigned through the group, you will need to inactivate them instead. To inactivate a trainee in the group, click on the green checkmark in the "Trainee Status in Group" column.
The page will ask you to confirm the status change.
After you click OK, the page will show that the status has been changed successfully, and the status in group will now be a red inactive icon. This user will no longer receive any future training assigned through this group.