You go to the site. You click on 'Download games'. You follow the instructions.
Then, most probably you say things like 'WTF?' and 'Where are the graphics?' and curse me for wasting your bandwidth. But anyone who loved real adventure games way back then is probably already downloading...
Actually, the narrative structure of the original Prince of Persia is VERY similar to Spider and Web, though this isn't immediately apparently until close to the end. So it's possible Assassin's Creed will take notes.
My favorite modern IF puzzle is probably the crystal maze in Photopia and its 3-letter solution, though I really enjoyed Lock and Key as the ultimate evolution of the fair--yet soul-destroying--Babelfish megapuzzle.
I thought the Babelfish puzzle required you to reload from an earlier save point since
the vending machine ran out of Babelfish just when you finally found out about the last obstacle.
Ah, I wish I'd managed to handle the Bureaucracy game, which felt like even more evilness.
Lock and Key was hellacious, though. And Photopia, though quite linear and not especially challenging, is really an amazing work; I highly recommend it.