Can I add tuition carryover amounts not on my original tax return?

I submitted my return but realized I forgot to include my tuition carryover amount from previous years (line 323). I can't add that line to my return with CRA My Account when I try and change my return for this year (it doesn't show up when I search it). Am I unable to amend tuition carryover amounts? Or do I need to file it by mail?