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.