No questions are stupid but - OE has fairly extensive help files and the following are straight cut and paste from the relevant sections that seem to answer both your questions!
"To add a contact to an existing group
In the Address Book list, double-click the group you want. The group's Properties dialog box opens.
You can add people to the group in several ways —and in some cases you can add them to your Address Book as well.
To add a person from your Address Book list, click Select Members, and then click a name from the Address Book list. Click Select, and then click OK.
To use a directory service (use the drop-down list at the end of the text box to see directories you have added to Outlook Express), click Select Members, and then click Find. Select a directory service to search, enter your search criteria, and when you find the person, click Select, and then click OK.
This person's name and e-mail address is added to your Address Book.
To add a person directly to the group without adding the name to your Address Book, type the person's name and e-mail address in the boxes provided in the lower half of the dialog box, and then click Add.
To add a person to both the group and your Address Book, click New Contact, fill in the appropriate information, and click OK."
"To move a contact or a group
In the Address Book contact list, select the name of the contact or group that you want to move.
Drag the contact or group from the list on the right to the group or folder you want it in on the left.
Contacts dragged to a group are added to the group, leaving duplicates behind in the original folder, but a group or a contact dragged to a folder is moved.
If you cannot see the Shared Contacts folder on the left, point to the View menu and select Folders and Groups.
Subfolders cannot be moved within an identity's folder list."