First check your gnome version:

$ gnome-shell --version
GNOME shell 3.36.4

Then go to location where your downloaded ZIP file, for me its Downloads directory.

cd ~/Downloads/

Get the extension UUID from metadata.json by this command.

$ unzip -c metadata.json | grep uuid | cut -d \" -f4

Or simply open metadata.json file and copy the UUID value. For me it is

Create destination directory for the gnome extension.

$ mkdir -p ~/.local/share/gnome-shell/extensions/

Unzip gnome extension file into the directory we made in the previous step, using this command.

$ unzip -q -d ~/.local/share/gnome-shell/extensions/

Then enable gnome extension with this command.

$ gnome-shell-extension-tool -e

if this warning gnome-shell-extension-tool is depricated, use gnome-extensions instead appeared, use the following command.

$ gnome-extensions enable

Don’t forget to replace the UUID of the extension with the one you want to install.

Note that the $ in front of commands means that this command is run as normal user. but # means that the command should be run as root using sudo.