If you are referring to social security
income, you need to enter it as social security on the foreign slip and
then the deduction will be calculated automatically. If it is from another
country:
From Easy step click on Forms and then the bottom left side there is "Forms" click and select T1 General Forms.
The scroll to line 256 and double click, this will take you to Additional Deductions and the line is called "Other income exempt under a tax treaty" and you can manually enter it there.
Read more in this
article: https://turbotax.intuit.ca/tips/what-is-exempt-foreign-income-6233
