In order to create a future purchase order for the next fiscal year you would need to follow the below steps.

Go to Core/Posting Periods and click on Create to create the July Posting Period.

If you don't have the posting periods between the month you are processing in and July already created you will need to create those as well.
Once July is open you are able to create a PO with a July 1 date.

When you create the June posting period, you will get the following informational pop up. Select OK.

Moving forward you can either leave all future posting periods open or you can close the future posting periods and continue to leave July open so you can continue to enter future Purchase Orders.
Please follow steps 3-5 if you want close the future posting periods.
Go to Report/Report Bundles to disable your monthly and fiscal report bundles, and any other report bundles that are triggered by closing posting periods if you do not want them to generate at this time.

If you don't have the ability to disable bundles, contact fiscal support and we can disable for you.
Go to Core/Posting Periods and click on the icon to close the posting period beside each month that needs closed, closing June last. You can leave July open if you want to continue to enter future POs.
Reopen the posting period you are currently processing in.

Your future encumbrances can be viewed in your Expenditure Account Grid.