This is the basic step of modding the game, not only for Resident Evil 4 Remake but there are more other games (Resident evil franchise, Devil May Cry 5, Soul Calibur etc) you could mod with this simple manager. It's light and easy-to-use. Thanks to FluffyQuack

• First, go to FluffyQuack official website[www.fluffyquack.com]
  
• Click Download button
  
  
• After the download completed, extract all files to anywhere you want to place it. Put it on desktop easier for me

Before installing any mods, make sure RE4 Remake's file directory already set up in Fluffy Manager, you can follow these step below

• Open Fluffy Manager folder and double-click ModManager.exe
  
• Click Choose Game then scroll down a bit and you'll find Resident Evil 4 Remake
  
  (i got 10 mods installed, so there's a number beside it)
  
• Click Choose Game Folder
  
• There are 2 options appear you can choose, both are fine. But i prefer Choose the game's executable
  
• Default installation destination is here "\Program Files (x86)\Steam\steamapps\common\RESIDENT EVIL 4 BIOHAZARD RE4\re4.exe"
  

This step is optional, you can skip it because not all mods require REFramewok. But most of best mods require this one, so you shouldn't skip it. This version is only for RE4, do not install other REFramework you've used to another game to your RE4 file directory.

• Download REFramework for RE4 Remake in Nexus Mods[www.nexusmods.com]or GitHub[github.com] for up-to-date information.
  
• Extract dinput8.dll into RE4 file directory.
  

Ensure that you check the website regularly for latest update.

After you've done installing Fluffy Manager, i'd recommend to install any mods from Nexus Mods[www.nexusmods.com] since it's safe and easy to download. You can go there and sign up first, it's worth it.

The example of mod i want to gave down below is replacing Leon's default skin to Ghost (Darkwater) from COD MW2. It's a great mod you can find it here[www.nexusmods.com]

• Download the mod and place RAR file or you can extract it into one folder (named it 'Ghost Darkwater' for example) .
  
• Place it in Fluffy Manager's file directory, manage to go Games > RE4R > Mods put it in here. It will looks like this screenshot below
  
  
• Open Fluffly Manager (Modmanager.exe)
  
• Click Choose Game and choose RE4 Remake, then you can see a mod you just installed it before. Activate or deactivate it by clicking the switch on the left side.
  

If you wanted to add another skin that replace the same Leon's default skin, then don't forget to activate only one of them. The game won't crash if you activate both of them, but the system will automatically chose only one while the other will be deactivated.

This step you only can follow up when the mod is requiring REFramework. I'll use Dodge Roll[www.nexusmods.com] mod (recommended mod for better dodge) for an example down below.

• Make sure RE4Framework installed.
  
• Download the mod and put RAR file into Fluffy Manager folder (\Games\RE4R\Mods)
  
• Don't forget to activate the mod via Fluffly Manager.

or you can install it without Fluffy Manager, just extract only folder "reframework" to RE4 file directory.