You can use the "Standard" version of the software to enter in your SS US pension. 

Here is the link to access it for the online version: https://turbotax.intuit.ca/personal-tax-software/online-tax-software.jsp

Or if you prefer the downloaded version here is the link: https://turbotax.intuit.ca/personal-tax-software/download-tax-software.jsp

Because we have a tax treaty with the USA, you are protected from being double taxed. 

Go under your Income tab - T-slips, at the bottom you will find Foreign Income, this is where you would enter your Social Security pension.