For a supercharged car:

1) Bring the car to operating temperature then turn it off and open the hood.

3) The 'hard' part of this is pouring the Seafoam into the center port you pulled the hose from.
To make it easier, take a water bottle and cut it in half. Puncture a small hole the size of the port opening near the bottom of the bottom half of the water bottle.
Using electrical tape, cover the puncture you just made. Now puncture a very small hole into the tape in front of the hole on the water bottle. What we are trying to do is make a diaphragm that the port can squeeze through but no liquid can leak out of.

4) Push the water bottle into the port and start the car. The car may idle oddly since we've created a vacuum leak.
Slowly pour some Seaform into the water bottle. The vacuum port will suck it up like the sucker at the dentist’s office. You want to pour 1/3 of the Seafoam into the engine but slowly so it doesn't stall.
When you are near the 1/3rd mark, pour more Seafoam so the engine stalls itself. This will let the Seafoam soak on the pistons.

5) Wait 5 minutes before restarting the car. As your waiting pull the water bottle from the port and reattach the tube. Clean up any Seafoam that may have dripped.

6) After 5 minutes have gone by you can start the car. The car might crank a few times before starting. After a few seconds you may notice some or a lot of smoke coming from your exhaust. This is the Seafoam burning off and is normal. Let the car idle for a few minutes, reving occasionally and then go for a drive to make sure all of the Seafoam is gone. The car may smoke even while driving, but it will go away. You may also notice the exhaust is slighly blue, this is fine as Seafoam is petroleum based.