See that score at the top...there's a surprise inside. Head on over the Stampin' Sisterhood to see what it is. There's a full tutorial there for you.
edited to add: After trying to insert this into a regular A2 envelope, I found that moving the card to the 1/8" inch mark on the Scor-Pal then scoring at 4 1/4" and 4 1/2" made it fit much easier.