Sludge in radiator.......

and where do you drain it from? do i just unscrew that wingnut looking thing at the bottom of the radiator? thanks again!

If you bought a Prestone backflush kit, did your read the directions"??

http://www.prestone.com/products/print.php?fam=12&num=2&name=Prestone+R+Flush+N+Fill+Kit&regTM=1

Overview
Professionally backflushes cooling systems of most cars and light trucks on the road today. Easily installs antifreeze/coolant in minutes.

Instructions

Install
Make sure engine is cool, then loosen radiator cap to release any pressure and re-tighten cap. If radiator has no cap, loosen and re-tighten the pressure cap on the expansion tank, if so equipped. If it has a conventional recovery system (a non-pressurized plastic bottle) and no radiator cap accessibility, vent and reseal the system via the cap covering the thermostat.
Two heater hoses extend from the fire wall to the engine, in both front and rear wheel drive vehicles. Hose #1 runs from fire wall to water pump. Hose #2 runs from fire wall to top of engine. This is the heater inlet hose. Ask a qualified mechanic if uncertain.

Back Flush

Make sure engine is cool, remove radiator cap and Flushing TEE Cap. Attach Back-Flow Preventer Coupler to Flushing TEE and water supply line (black end to tee, Yellow end to garden hose). If vehicle has no cap on the radiator, it is possible to back flush by disconnecting the upper radiator hose at the radiator.
When appropriate, snap Splash Tube into radiator neck and open radiator drain. Turn on water to garden hose. Check to see that liquid is emerging from the Deflector Tube or radiator hose fitting before proceeding.
Fill

Determine how much Prestone® Antifreeze/Coolant to install to achieve a minimum 50%, maximum 70% solution for year round protection.
With cap off TEE, pour the full amount of Antifreeze/Coolant into radiator, expansion tank, or thermostat housing opening. Water and slight amount of diluted Antifreeze/Coolant will be displaced from flushing TEE.
After adding antifreeze/coolant, quickly replace Flushing TEE Cap. Make sure gasket is in place. Tighten securely by hand. Replace radiator cap.
Run engine for 10 minutes after reaching normal operating temperatures, then shut engine off and allow to cool. Add more Antifreeze/Coolant to properly fill the system. Replace cap tightly.