I have always sucked seafoam through a vacuum hose on the intake manifold utilizing a stock hose, with the engine running. Depending on which hose you use you may need to cap the port left open by the hose you are using. I use one of the ports on the throttle body or on the plenum of the manifold. iirc the instructions on the bottle say to use half a bottle (8 oz) per cleaning. After 8oz have been sucked into the engine, shut it down for a few minutes to let it do its magic then start the engine and conservatively bring the rpm up (2-4k rpm) and wait till your exhaust is clear again (it will be thick white smoke for a while) I recommend thinking about where you do the treatment due to the quantity of smoke and noise of reving the engine, I have used out-of-the-way parking lots mostly. It takes me 15-20 minutes on average to clear the engine of the seafoam. Hope this helps!
~Brian A. Moreno