A man named Daniel sets up cameras to record his girlfriend, Shelly, who is exhibiting disturbing, supernatural behavior.
Step 1: Use standard weapons (pistols, SMGs) to wear down their health until it's in the red.
If you meant a guide for the (which was recently Remastered in HD), here are the core mechanics to master:
Fix: Use Adrenaline shots to calm them down or move them to a well-lit, "safe" area.
Gain trust: Give them weapons, ammo, or heal them with health packs.
You cannot kill "Things" with just bullets.