My employment is 100% remote. Where do I enter the rent for my apartment, of which I use 1/3 for office space?

Here is where do you can claim your employment expenses: https://turbotax.community.intuit.ca/replies/2647650

If you have TurboTax Live Assist & Review, here is how to talk to a Tax Expert: https://turbotax.community.intuit.ca/replies/3456106