It can be done but is so cost prohibitive that you are better off to trade it in or sell it and buy a manual.
In addition to the obvious which is the transmission you need clutch pedal assembly, clutch disc, pressure plate, throwout bearing, flywheel as the manual is different than the auto on most cars, transmission mounts, clutch master cylinder, assorted lines for fluids, possibly a new ECU/ECM and several other bits and pieces that are too many to list here. Depending on where you get everything you are looking in the ballpark of $4000-$9000 not including labor to actually do the work. That is a lot of money to put into a car with nothing to show for it other than a shifter that moves East and West as well as North and South.
If you want a manual that bad, sell it and buy a 5 speed or take the many thousands of dollars you would put into changing it over and buy a second car that is a stick.