Obviously a different card but dimensions are the same. Lay your card in the center of a 12x12 sheet of scrapbook paper. With the card being 5 inches wide that leaves you with 3.5 inches on each side of the card. I had folded this already when I decided to grab my camera and provide a tutorial so unfolded it so I could get some more shots.
Now you will trim out the corners on the top and bottom of your folded paper. See the bottom cuff corners I cut out? If you look at the 2nd picture I posted you will see the corners and how I trimmed them out in the above picture. Do this to the top cuff too. That way you won't have several layers of paper folded over to glue down. Your finished envelope will look much nicer. After you've made your corner cuts you can use a corner punch to round the bottom cuff if you wish.
Refold your flaps and glue down your side flaps first, then bottom flap. You should have nice smooth seams. Wait until the envelope is dry before inserting your card. Once your envelope is dry you can put your card in and glue down the top flap sealing your card inside. If you use patterned paper as I've done here and are planning on mailing your card you may need to make labels for the front of the envelope for the address and return address so they are readable by the post office.