You can find the Silhouette file here
It is a small card but if you select everything and drag the corner to re size, you can easily change the dimensions.
After cutting out, apply adhesive to the inner frame, including the letters and stick some plastic over the window. (There is a rectangle for this in the file).
Apply double sided tape to the outer edges of the front of the card (the folded part).
Pile some hearts or sequins in the centre, away from the tape. Remove the tape backing and carefully, line up the window of the card with the front of the card.
Quick and easy! Use whatever colour theme you wish and if you want to go overboard on decorations then feel free!