Choose the album you want to make (its easier if you actually have the album, but it doesn't matter too much). Find and save a picture of it online.
Crop out any specific images from the album cover that you want to customize. I decided to change the logo on the girl's shirt of Kerplunk. I like to use Picnik photo editor to crop, but anything works.
If you've decided to edit any images of the album cover, use Paint to edit.
Open Microsoft Word, or any notebook software. Paste in the image(s) that you edited. Look for the font used on the album online (most Green Day fonts are at http://www.greendayauthority.com/downloads/fonts.php ). Type up the motto you want, I just used Happy Birthday Megan.
Print off the card cover, and cut out. Fold the coloured card in half, and blue-tac on the cover.
Cut around the cover, and glue it on
Write the inside of the card. I chose a lyric from the album that I liked, and wrote that in.
Finish any other parts of the card. Now you're done! ^_^