Welcome to QuickBooks Online, John! I will guide you with your tax filing.
First, you'll want to set up your VAT in QuickBooks, so you ca assign VAT codes to your transactions.
Second, you'll need to enter your transactions with tax codes assigned to them, so they'll show up on your VAT page. To do this, you can either connect your bank account to download your transactions and add them to your books, or enter them one by one. You may check out with an accountant for alternate ways to enter your transactions with taxes.
Third, you'll want to enable MTD filing in QuickBooks and authorise it to interact with HMRC. Please be sure to sign up for MTD filing in the HMRC website first before authorising QuickBooks.
Fourth, submit your VAT return.
You can always go back to this thread if you have other questions about filing.