requirements:

Make sure your device has a dedicated GPU (Nvidia / AMD cards) to be able to run the pack perfectly with shaders. Running the pack with Intel integrated GPU may crash your Minecraft due to some graphical features used by the pack via OptiFineHD.
It is recommended to have at least 8GB of RAM in total in your device in order to run it perfectly with shaders although you can still run it with lower amount RAM.

Preparation:

• Download and install OptiFineHD. This will create a new profile in your Minecraft launcher. Run the .jar file as if you open an .exe application.

OptiFineHD: https://optifine.net/downloads

• Download the shader of your choice and copy the downloaded .zip file to the shaderpacks folder in your Minecraft folder. If the folder doesn’t exist simply create it (see Folder locations below). NAPP is recommended to work with BSL Shaders.

Shaders & Alternatives:

(RECOMENDED) BSL Shaders: https://www.curseforge.com/minecraft/customization/bsl-shaders

AstraLex: https://www.curseforge.com/minecraft/customization/astralex-shader-bsl-edit

Complementary: https://www.curseforge.com/minecraft/customization/complementary-shaders

Sildurs: https://sildurs-shaders.github.io/downloads/

Continuum: https://continuum.graphics/downloads/

SEUS Renewed/PTGI: It is available through Sonic Ether’s website.

Optional: Go to the settings of the OptiFine profile inside your Minecraft launcher (Installations → OptiFine) and allocate more RAM (MORE OPTIONS → JVM ARGUMENTS → change the 2 in -Xmx2G to half of the amount of RAM you have, say you have 8GB in total, so change it to 4). This could improve your performance.

Note: Do not allocate too much RAM, otherwise Minecraft starts using too much RAM in the background.
Download NAPP and copy the downloaded .zip file to the resourcepacks folder.
Now start Minecraft.

• Enable Resource Pack and Shader:
  Options → Resource Packs: select NAPP 3.0 512x.zip
  Video Settings → Shaders: select the downloaded shader

Default Folder Locations:

Minecraft: C:/Users/[Username]/AppData/Roaming/.minecraft
Shaders: C:/Users/[Username]/AppData/Roaming/.minecraft/shaderpacks
Resource Packs: C:/Users/[Username]/AppData/Roaming/.minecraft/resourcepacks

Hint: You can get into the “Roaming” folder really quick by opening the Windows Start Menu and type %appdata%. Hit enter.

Shader settings (BSL Shader 8.1 Preview 1):
Options -> Video Settings -> Details -> Alternate Blocks: OFF
Options -> Video Settings -> Quality -> Connected Textures: Fancy or Fast
Options → Shader Settings → Shader Options →
Material → Advanced Material: ON
Material → Material Format: SEUS/Old PBR
Material → Normals & Parallax → Parallax Occlusion Mapping: ON
Material → Normals & Parallax → Parallax Depth: 15cm to 20cm
Material → Normals & Parallax → Parallax Samples: 128 to 512
Material → Normals & Parallax → Parallax Distance: 32 or above
You may tweak other settings to your desired preferences.
View #shader_settings on our official discord server for other possible 3D settings and comparison.

Compatibility:

NAPP resource pack is currently set for 1.13+. However, if you encounter compatibility issue message in newer version of minecraft, we suggest you to just ignore that. We have tested it on 1.15 and 1.17 (with OptiFine of course). It works well for as long as you are using the right shader with the right settings (1.17 of OptiFine is still under development, so you can expect some low fps or other issue. Be sure to report them on our official discord server). Minecraft of versions lower than 1.13 would require some tedious work to make it work which is not the main focus at the moment.