1. You print it. If you often experience curling problems, this print will surely curl due to its large, flat first layers. I recommend printing using a raft with no margin. The wallet prints near the edges of some beds, so there is not much room to spare.
2. You lid it! Pick your favorite card to use as a lid. Photo ID is great for quick reference. Slide it in the top.
3. Put other cards inside! Put the long side in first and it will easily drop in to place.
4. Load it with whatever you'd like!

To remove cards easily, tip to one side and push your finger through a hole in the bottom. (Don't worry, holes are smaller than an American dime.)