You can find how to upholster the headboard here.
This was actually a really easy project and took about an hour from start to finish. If you already have a box spring the cost is next to nothing. By upholstering your own box spring you can make a fully upholstered bed.
Our box spring was a twin so these are the measurements we used. You'll have to sew together a couple pieces of fabric to wrap around the box spring. Our fabric was 45" wide x 60" long. We cut it in half at 22.5" wide. We then had 2 pieces that were 22.5" and 60" long.
At this point pin the two 22.5" pieces together on one side. For a total length of 180".
Sew down this line with a zig zag stitch. We also sewed down the edges of the fabric to prevent fraying.
Now drape this over the side of you box spring, making sure you have enough room to staple on both sides. Pull taut and staple as you go.
Continue wrapping around the full box spring. We found it easiest to have one person hold the fabric and one person to staple.
Now I know my corners don't look pretty, but I'm not a perfectionist if you are I'm sure you can make prettier corners. But it doesn't really show, we just folded them under and stapled like crazy. It worked for us.=)
When we got to the end we made sure the ending point would be against the wall. We tucked it under and you can still see the line. So if that is something the bugs you make sure to put that area next to the wall.
If you want you can also add feet to make it look more like a "real" upholstered bed. It's a really simple project and I highly recommend trying it!