You can choose command as per your linux distro i am using fedora so i am using dnf if you are using ubuntu then you have to apt
sudo dnf install zsh
sudo cp -Rf zsh-* /usr/share
sudo cp -Rf .zshrc ~/
sudo chmod 755 /usr/shard/zsh-*
type -a zsh ## find path to ksh ##
chsh -s /bin/zsh ## change bash to ksh ##
grep "^${USER}" /etc/passwd ## Verify if changed ##