let your engine run while slowly letting the vaccum from your pvc valve suck the seafoam in while your pouring. be careful not to pour too fast as it will kill the engine. When i did mine... when i had gotten to the end of the bottle poured it in fast to kill the engine on purpose. It says after it kills the engine to let it sit for 15 to 20 min's.... I guess so it can do its thing removing the carbon in the combustion chamber and all... then start it up and get ready for the smoke show. I'm pretty sure it works... there's alot of fans of the stuff just like lucas oil.
Not sure if this is the best way to do it but its how I did mine and got pretty good results.