To claim you expenses (and income), you would use Form T2125. There are different ways of accessing it depending on which version of TurboTax you are using.
If you're using TurboTax Online:
Click on “Self-Employment” under the Income tab.
You can also click on the “Find” icon in the top right and search for “Self”. Select “Self-Employment” and then click the “Go” button.
If you're using TurboTax CD/Download:
If you are using the EasyStep Interview method, click on the “Find” icon in the blue menu. Search for “Business”. Select “Business Profile” and then click the “Go” button.
If you are using the Forms method, click on the “Forms” icon in the blue menu. Search for “T2125”. Select “T2125 P1” and then click the “OK” button.
As to how to how to keep track of expenses, this would be something you need to look into. There are a lot of books and websites that talk about things like Cost Of Goods sold, keeping track of inventory, etc. You may also want to look at software like Quickbooks, which will not only help you track expenses, but will also help you keep an eye on your income, time spent on projects, etc… https://quickbooks.intuit.com/ca/