Sadly it is hard to find help for some of the more obscure games here.
You need salts as far as I recall. You should be able to get info from a ghost behind the demon door, under a bed. I think the ghost will tell you to use some salts to get rid of the (four pentagrams, well, five counting the one that will send you to the next part of the game).
Not sure if you need to see that scene to trigger the "ability" to get rid of the pentagrams with the salt or just the item "salt". I would beat the demon door just in case (good experience and pictures are worth like 150 to 300) and see the scene just in case.