What do I need to get a canadian visa from nigeria? I have a good job

Visit the Canadian embassy in the city nearest where you live and apply for one.

You can go to the website below, there is a survey that asks you about work experience and education, you get points in each category and if you have enough points at the end it will tell you you are eligible to apply for a work visa. I don't see this survey on the website anymore but this will give you a good start.

Working temporarily in Canada: Eligibility to apply (http://www.cic.gc.ca/english/work/apply-who-eligible.asp)