Currently, we cannot add VAT into QuickBooks Self Employed. This only available on our small business packages (QuickBooks Online).
You may consider creating a new subscription for QuickBooks Online, you can go directly to this link. Then, choose a plan you want to use for your business. The program also offers a free one month trial. For the discounted price, click the Buy now & save button.
Then, you can either connect your bank or upload CSV files for a quick way of re-entering old transactions. Check the links below for more details: