In case you want a little more detail...
You follow the "action procedure" for any optional actions (as in any phase):
"As the Free Peoples player, you get the first opportunity to perform an action, and then the player on your right gets an opportunity, and so on counter-clockwise around the table.
If a player does not wish to perform an action, he may simply pass. Passing does not prevent a player from performing an action later in the same phase."