If you only have the .tt24 file, then you need to have the program installed to open it, which means getting a licence.

If you don't have access to the Canada Revenue Agency’s (CRA) My Account service 

to look up your past year's tax information, then you can contact them to ask for a copy of your return. If you are in Canada or the United States, you can call the CRA at 1-800-959-8281. If you are elsewhere, you can call 613-940-8495. This page has more ways to contact the CRA: Contact the Canada Revenue Agency