This Guide is only supported for Minecraft 1.15.2 and newer.

Before you start the installation, make sure that there is no Game or Launcher running.

To install the mod, simply double-click the jar you downloaded and select the folder where you want to install it followed by clicking on Install.
On the next screen can you now select other mods that you want to install too, or continue by clicking on Install again.

The game should now be installed and a new 5zig Reborn Profile should be available within the Launcher to select and execute.

Troubleshooting

If you get a prompt similar to Choose a program to open this file and there is no Java option to select, make sure to download and install Java and try again.
If however, the double-clicking of the jar opens it in 7Zip or WinRAR, close the window and right-click the Jar followed by Run -> Java (May look different depending on your OS and version).