Help on CAN Immigration,Please

I am in the States and want to apply for CAN immigration; however, I am really confused about what documents to show as proof of employment in the US. I don't want to go back to my previous employers for letters of reference, can I use other documents as substitution, such as W-2 or paystubs. My job was accountant before.

Also, can someone give me a website or chat group where I can learn more practical help on how to prepare these documents. Thanks!