I am a US resident but now live in canada and got income from my T4. Where do I enter that on my US 1040?

You enter it as foreign earned income on Form 2555.

To enter Foreign Earned Income -

Click on Federal Taxes (Personal using Home and Business)
Click on Wages and Income (Personal Income using Home and Business)
Click on I'll choose what I work on (if shown)
Scroll down to Less Common Income
On Foreign Earned Income and Exclusion, click on the start or update button