Is there an address for Skylar Astin??

I sent an email on his site http://www.gordonramsay.com requesting an autograph on August 31st. Received a signed 14.8cm x 21cm photo on September 7th.

photo:



mail:

I know this is going to sound extremely weird, but I have never mailed a letter in my life before.

I'm interested in mailing to a celebrity (Shay Mitchell) in the USA, from Canada.

Do I put Canadian stamps on the envelope and USA stamps on the SASE? How many should I put?