Hi,
If you are in Turbo Tax desktop select income and expenses, then Tslips below. You may need to check the box for T4A on the list. Then T4A should appear below Tslips. To edit a slip select T4A under Tslips and click on edit next to the slip or to add a new slip click "Enter new T4A".
If you are in Turbo Tax online, select Income at the top bar, then Tslips, then T4A. Then select edit next to the T4A slip or select "Add new T4A."