Hi,
The Post Office asked for a Canadian address to open a PO Box. I did not have that so they setup a "General Delivery" under my name. So if you are unable to open a PO Box, ask them about "General Delivery".
Also note that the "General Delivery" address is quite long, it does not fit the SIN system, so ask the Post Office for the shortest address which would work. I used something like "GD" for "General Delivery".