I live in the United States so would I need stamps for the U.K.? If so where can I get some

Hi I'm new to this and live in the United States. I want to send an autograph request over seas to London but have no idea what I have to do to get it back. People are saying I need to buy British stamps. I don't k ow please help.

Hey congrats on the success! Is there a chance you could message me. I wish to write a letter like you except have no idea what to do and how to send it thanks!