Thank you for using TurboTax. From the left side panel, when you select "Income" > "Self Employed Income." Filing in the T2125, after the income section is the expenses section "Expenses (enter business part only)" This section can be used to enter all the expenses used for the business throughout the year.
As per CRA, for 2021 tax returns you can also calculate business-use-of-home expenses. Expenses you can claim