To edit the contents of an array you first need to change to the variable window. The quickest way of doing this is by pressing <ALT><3> and using a combination of the ↑ or ↓ keys to move the highlight bar to the variable which contains the array that you wish to edit and press ◄──┛.
You will see a box similar to the following appear:
You may move the highlight bar down and up using the ↓ and ↑ keys and press ◄──┛ to edit one of the items of an array. If the item that you choose to edit is another array, then another array will appear for you to view or edit as you see fit.