The "Billy" model is a basic bookshelf kit from IKEA, it comes in a wide variety of sizes and colors. This kit is straightforward to assemble, a good kit for novices in the smaller sizes. I've followed along exactly as shown in IKEA's instructions included in the kit, but here we have the advantage of close-up photos and photo-notes. The other sizes and colors of this model assembly nearly identical to the one shown.
Step 1: Step 1 - identify the parts, start assembly
1 back panel
2 side panels: 1 right side, 1 left side
4 shelves: 1 bottom, 1 top, 2 middle
bag of hardware
2 unused small wood pieces
anti-tip-over "earthquake" strap
start the assembly
Insert 6 of the wood plugs into the side panel holes with your thumb. 2 of the plugs are used for the bottom flashing, 2 for the bottom shelf, and 2 for the top shelf. use the outer holes on the side panel as shown.
The 4 shelves are each slightly different, you can tell them apart by looking at the bottom of them as shown in the photo.
carefully push the bottom flashing, bottom shelf, and top shelf onto the plugs in the side panel, as shown in the photo.