Here on the Enroll and Resign tab you can add your group members to the group registration.
Click "Add" next to your members under the header:

And they will be added under the header:

Here you select the fee your participants should have. This will in turn have an effect on what extra questions should be answered for them.

This is the questions that needs to be answered connected to each participant in your group. Select edit to open the form and answer the questions.

Select save and close when you are done with the current participant. When the form is closed you will go back to the Enroll and Resign page.

Do this for each particpant.