Step 1: Bringing them together
Rip open the innards of the solar garden light. I know that may sound ambiguous but you'd be able to use a utility knife and surgically dissect the relevent components out (see image). Solar garden lights are easily available at your local major hardware store. If you're in Australia, try Dick Smith Powerhouse.
Flip open the ikea jar and place the "solar garden light innards" as shown in the picture. Use blu-tack to keep it all together. Feel free to play around with the placements so the components would fit snuggly into the jar.
Cut a strip of tracing paper and place it in the glass jar.
Use a Glass Frosting spray .
Close the lid of the glass jar with tender care and you're done.