In order to access the tools you could use a pop-up menu. For tools that you can “equip” or constantly use, use a game overlay instead.
EMF Detector: Easy enough, you can use a pop-up to display information and use blocks to make it display different information when the ghost’s activity level is changed.
Night vision cameras/headgear: Use this guide. The darkness should be on by default but obtaining the equipment will deactivate the barriers.
Crucifix: Depends on what you’re using for the ghost. Just make it deactivate the ghost’s mechanic that allows it to hunt.
Book: Same thing with the EMF detector.
D.O.T.S Projector: Make it activate sentries/props.
UV Glowstick: Same thing with the projector.
Flashlight: I would say just let the player have this by default since it correlates with the guide I linked.
Smudge Stick: It’s pretty close to the Crucifix, so perhaps make it so the ghost isn’t as effective at hunting.
Sanity Pills: Make the sanity similar to something like a breath meter or hunger bar, and the pills will increase the sanity.
Spirt Box: Same as the book? I’m assuming that it involves a physical item of some sort so maybe have it grant an item or do the same thing as the book.
Salt: Same thing as Smudge Stick, but after you run out the ghost will be more likely to find you if it has previously gotten close to you while the salt was active.
Lighter: Same with flashlight.