I hate the stuff, but I know it's pretty popular on other forums I am on the best way to add it through a vacuum line is as follows:
Unhook brake booster vacuum line and pour slowly into it, letting it suck it in. You will see smoke.
Then pour more at faster rate (will stop the engine). Don't restart, let it sit for a while. Restart.
Pour the rest in the gas tank the n change your oil/filter
Be extremely careful when adding it to your crankcase, it will thin your oil quite a bit an over time can cause bearing issues. If I were to ever run it in my oil I would only go about 200 miles at the most on it if that and change the oil and filter after.
If you're wanting to add something to the crankcase to clean your engine add 1/2 quart of ATF into it, drive it a little then do an oil and filter change...ATF is very high in mineral spirits and is an excellent cleaner. It is even used as an injector cleaner/pump lubricator in diesel engines, when a little bit is added to diesel fuel.
I wont add anything into my fuel but Berrymans B12 Chemtool...IMO and from working for an oil company for the past 11 years who also makes engine chemicals, Berrymans has more cleaning agents in their blend than anything on the market.