If you have selected local area pass and you would like to upgrade to a full area pass in resort, you will need to speak to the lift pass office in resort and they can advise you on the availability and cost to select this.
If you are looking to downgrade your lift pass this would not normally be possible.
The advice before making any changes or speaking with the lift pass office is to make sure your lift pass is unused, as once it has been used on a lift, the options available for changes becomes limited