First search for the contact in Contact Widget

Next click the toggle check box button

This will enable check boxes next to the contact(s), and display a row of buttons to perform actions on the checked contacts.

To copy a contact(s) into a group, first tick the box next to the contact(s) you want to copy, then click the copy button.

A dialog window will open. Select the group you want to copy the contact(s) into. tick the box next to the group name.

Finally, click the Copy To button

If you switch the group to the one you copied into, you will see the contact.