If you'd like to change the shipping address associated with your Stix subscription, you must have created to a Stix Account. That's where your subscription is managed. Here is an article on creating and activating a Stix account.
Once you have an active account, here are the next steps: (edited)
Log into your account by visiting our website at getstix.co and clicking ‘Log In’ on the upper right corner of the homepage.
Enter your account credentials and click ‘Sign In’.
Once you’ve logged in, scroll down to 'Settings' and click ‘Change Address’ under your shipping address.
From there, you can add a new address or select a previous address. Note: Please be be sure you select 'Set As Default' after making your new selection.
As always, we’re here to help at firstname.lastname@example.org.