To change your financial year end you’ll need to head into Xero, Settings > Financial Settings, make the change, and then run a sync to Figured once saved.
Please note that you cannot change your season end (i.e. the annual basis that your planning tab runs to).
Your season end is configured at the start of your farm creation and it affects the data you’ve already entered into your Figured file. A new farm must be created if you wish to change this season.