Many forms on this site use a combination of select boxes like this:
The box on the left are those items chosen. The box on the right are available
items that have not been chosen.
To choose an item select it in the right-hand box and click .
To removed a choice, select it in the left-hand box and click .
Alternatively, selecting one or more items in the right hand
box before submitting the form will also work. To select more than one option,
hold down the ctrl (apple) key and click.