You need to claim the tuition in the same year you got the T2202 slip for. So if you have a T2202 for 2017, then you need to go back and add it to your 2017 tax return.
If you have a CRA My Account login, then you can check there what tuition you’ve already claimed. You can login to the CRA's My Account here: https://www.canada.ca/en/revenue-agency/services/e-services/e-services-individuals/account-individuals.html
You can make changes after you have filed your tax return through the Canada Revenue Agency (CRA) or through ReFILE. This FAQ has more information: https://turbotax.community.intuit.ca/community/tax-return-amendment/help/i-have-filed-my-tax-return-can-i-still-make-changes/00/873608