In this video, we have explained to you that how you can download, install and customize themes on linux mint. Many popular themes for linux mint are available on the GitHub. We have downloaded three themes from the GitHub and installed them on linux mint system. Commands that are used in this video.
sudo apt-get install gtk2-engines-murrine gtk2-engines-pixbuf
sudo chmod +x install.sh
sudo apt install arc-theme
sudo chmod +x install-gtk-theme.sh