If you are claiming employment expenses because you worked home due to COVID, you need to confirm this on your T4-slip entries. On your T4-slip page, answer "Yes" to the question at the bottom so it takes you to the Employment Expenses Profile.
If you are claiming regular Employment Expenses because you have a signed T2200 from your employer, access the Employment Expenses Profile from the left-side menu under "Income". Then check the scenario that applies to your tax situation:
I hope this was helpful