Actually, there is no “work from home tax credit”. Instead, the CRA has temporarily introduced a flat rate method of claiming expenses related to working from home, up to a maximum of $400. You can see how much of the deduction you are getting by looking at line 22900 Other employment expenses on your detailed tax summary.
This FAQ shows you how to get to the Detailed Summary in TurboTax Online: https://turbotax.community.intuit.ca/community/tax-return-status/help/how-can-i-see-a-detailed-summary-of-my-return-in-the-online-edition-of-turbotax/00/873513