It depends. If you are self-employed, you can claim your Expenses in the “Self-Employment” section of the interview. Click on the “Find” icon in the blue menu and search for “self”. Select “Self-Employment Summary” and then click the “Go” button.
If you are employed and you have a T2200 Declaration of
Conditions of Employment form from your employer, you can claim any expenses
that you haven’t been reimbursed for (that are on the T2200). https://turbotax.community.intuit.ca/replies/2647650