Prerequisites
Java
Go to https://www.java.com/en/download and click the “Download Java” button to download, then open the downloaded installer and follow the installer instructions to install.
Mod
Optifine
Go to https://optifine.net/downloads and download optifine for your desired version by clicking on “Download” button, after waiting for a few seconds click skip on top right corner which will lead you to the final real download page and click on the "Download" button once again.
After downloading double click on the downloaded optifine.jar file and click "Install", Click on the "OK" button on the successful installation popup to close the installer.
Resource Pack
Installing resource pack
Assuming you already have downloaded your desired resource pack, move the downloaded resourcepack.zip file(s) to the resourcepack folder in your .minecraft directory, then in-game go to Options > Resource Packs..., select the resource pack(s) on the left side to load them, active resource packs will appear on the right side.
Shaders
Choosing the right shader
For any of my resource packs it is recommended to use a fully LabPBR compliant shader, here’s a list of LabPBR shaders to choose from https://wiki.shaderlabs.org/wiki/LabPBR_Supported_Packs.
After downloading the desired shader paste the shader.zip file in your shaderpacks directory.
Now in-game go to Options > Video settings > Shader packs... then select the downloaded shader and click apply.
Configuring Shaders
Shader settingsShader settings
In order to achieve screenshot like results we need to change some shader settings, to find the recommended settings for your desired shader please move to the shader settings page.