Hi @loanedwolf - Trent here from TurboTax to help!
If the income reported on your T4A slip is related to a Self-Employment income you will have to complete a T2125 Form (Self-Employment Income) and there you can enter all the expenses and other information that are required to complete your return.
Here are some links that might help:
https://www.canada.ca/en/revenue-agency/services/tax/businesses/topics/sole-proprietorships-partnerships/report-business-income-expenses/completing-form-t2125.html
https://www.canada.ca/en/revenue-agency/services/forms-publications/forms/t2125.html