Hi,
You will need to enrol for the Making Tax Digital service in order to complete your VAT returns.
If you sign in to the account set up to apply for VAT registration you will see an option to add taxes and schemes and this is where you will enrol for the Making Tax Digital service.
Sign in to your VAT online account
This will then confiirm what your VAT submission periods will be and the first one will very likely be the first 4 years of your registration.
Thank you.