SIN number

I understand I need something called a SIN number if I wish to work in Vancouver.
Can someone tell me exactly what one odoes and how I can obtain one? Is it possible to get one online, before I leave?

An elementary google search reveals this

Shouldn't it be SI Number, or just SIN? Why the extra N??

#2, reminds me of when people say ATM machines and PIN numbers

According to wikipedia, htis is a case of RAS Syndrome:
"Redundant Acronym Syndrome Syndrome,"
wikipedia.org/wiki/RAS_syndrome