Yes, and both are correct in that you have to go to the post office to get one and it is an international stamp for the country you are sending it to.
In the U.S., international letters can be sent from home without international stamps. This link tells how - http://pe.usps.gov/text/imm/immc2_018.htm
I would have said just use email, but I know how nans are with computers But I don't know, if it was anything like how you send one from the UK you just need to correctly stamp the thing.