I want to install icon theme in gnome desktop.Please help me.
You can use pacman to browse every package from the official repos, for example:
pacman -Ss icon theme will search for the terms “icon” and “theme”.
To install a package, issue:
sudo pacman -S name-of-package.
The new theme(s) will show up in Gnome’s dedicated settings.
You can also get them from here, and then place it at ~/.icons.
You will be able to find the ones you have installed in the Tweaks app under Appearance>Icons.