If the Canadian pension that you have is similar to a company pension plan:

Enter your company pension income as a 1099-R in US dollars. Enter the Canadian tax withheld as a foreign tax credit in Form 1116. The TurboTax section for Canadian Registered Pension Income is a worksheet for RRSP and RRIF income. If you have ever filed Form 8891 in the past, your RRSP will now be a worksheet. But in the end, all 1099-R and RRSP worksheet totals get added up on line 16a and 16b on Form 1040.

If the Canadian pension that you have is similar to U.S. Social Security system, see this article:

https://ttlc.intuit.com/replies/5334341