ElvUI is an exclusive user interface for World of Warcraft that enhances players' gaming experience with the ability to upgrade, configure and customize current versions of WoW. To install ElvUI, you need to download the interface from the developer's website and then move the files to the "Add-ons" folder in WoW on your computer.
Steps
Part 1 of 2: Installing ElvUI

Step 1. Visit the official download page of ElvUI at
ElvUI is available to all WoW players from members of the Tukui WoW community.

Step 2. Click 'Download' under ElvUI, and select the option to save the.zip file to your desktop

Step 3. Go to your desktop and double click on the ElvUI.zip file to extract its contents

Step 4. Open the 'World of Warcraft' folder on your computer using File Explorer in Windows or Finder in Mac OS X

Step 5. Open the 'Interface' folder and then the 'Add-ons' folder

Step 6. Click back to your desktop and copy the files named 'ElvUI' and 'ElvUI_Config' previously extracted from the.zip file

Step 7. Paste these files into the 'Add-ons' folder in your WoW folder

Step 8. Start your WoW game and then go to the character selection screen

Step 9. Select 'Add-ons,' then 'ElvUI.

Step 10. Select the option to start your game
You can now follow the instructions in ElvUI while playing to enhance your WoW gaming experience.
Part 2 of 2: Troubleshooting ElvUI installation

Step 1. Try the Tukui Windows Client instead of the Curse Client, if you are using the program to add ElvUI to WoW
The Tukui Windows Client is designed to help you manage all add-ons downloaded from the Tukui website, while the Curse Client no longer fully supports add-ons from Tukui.

Step 2. Return to the ElvUI downloads page at https://www.tukui.org/download.php?ui=elvui and download the latest version of ElvUI, if the interface stops working properly
In some cases, ElvUI may falter if a newer version of the software exists.

Step 3. Check that your ElvUI files are not in an extra folder in the WoW 'Add-ons' folder
Placing the ElvUI files in additional folder may prevent ElvUI from loading properly during WoW gameplay.

Step 4. Make sure to extract the ElvUI files before trying to move them to the WoW folder on your computer
If your computer doesn't have a default unzip utility, download one like WinZip, WinRar, or 7zip for your Windows computer, or The Unarchiver or StuffIt for Mac OS X.

Step 5. Quit WoW and relaunch the game, if the ElvUI add-on is not listed in the 'Add-ons' menu
In most cases, WoW will not register changes to add-ons until you exit and restart the game.