Stir the mixture occasionally until the solution drops to about 15C or lower. This will take about 30 min. If you wish to speed this up, you can use less water to dissolve the tablets, and add ice chips to cool the mixture faster. Just make sure you don't add so much ice that you drastically increase the volume of the mixture. Filter the solution using whatever you have.
Coffee filters work well, but lab filters work the best.
Just make sure you don't end up with obvious solids in the filtered solution. This will take about 1 hr. You may also want to rinse the solids left over in the filter with some ice-water to extract any remaining codeine. Sit back and wait for the effects. Because the codeine is already in solution it only needs to be absorbed, while codeine in the tablet form must dissolve before being absorbed.