Unfortunately, there is no way to change the year of a tax return. You'll have to re-do your 2019 return in the right year: https://ww1.2019.turbotaxonline.intuit.ca/
You’ll also need to contact the CRA and ask them what you need to do since you’ve filed the wrong information for 2018. You can call them at 1-800-959-8281.
