https://www.gov.uk/government/publications/making-tax-digital-how-vat-businesses-and-other-vat-entities-can-get-ready/making-tax-digital-how-vat-businesses-and-other-vat-entities-can-get-ready

Making Tax Digital starts in April 2019 for VAT registered businesses with a turnover of £85K or above.

This means that you can no longer file your return via HMRC's website.

MTD applies to the first quarterly period starting on or after 1 April. So the following applies:

April quarter - file via usual way
May quarter - file via usual way
June quarter - file via MTD

There is various software available, along with bridging apps if you want to use spreadsheets, although I recommend software as being the best way forward for MTD.