Firstly you need to install
https://optifine.net/homeYou will get a java application and you have to open it and install it. After that is quiet simple.
"1. Install
Optifine first2. Run Minecraft.
3. Navigate from “options” > “Resource Packs” > “Open resource packs folder”.4. Download the
XRAY Texture Pack from the official links
5. Drag and drop the Xray Ultimate
(.zip file) into the folder that just opened.
If you don’t want/need to install Optifine just don’t do it."
I really don't like "x-ray" but your choice.
