pacman -S zsh
In the image it shows reinstalling, because I already have it, but so that you can see at least what it installs.
2 .: Once installed we are going to transform it into our default terminal in this way:
ice@ice ~$ chsh -s /bin/zsh
3 .: Then they will surely have a configuration "wizard", they will follow it if they want step by step by selecting the letters and reading what appears or else cancel it and directly continue with step 4 like this ...
4 .: Let's now install oh my zsh, with yaourt:
ice@ice ~$ yaourt oh my zsh
As it appears in the image, we select option number "3". We do not edit anything and then directly we interact as we are used to yaourt.
5 .: Once installed we are going to configure it by copying the zshrc file to our home like this:
ice@ice ~$ cp /usr/share/oh-my-zsh/zshrc /home/ice/.zshrc
6 .: In .zshrc as in .bashrc, we can enter, for example, with nano to edit it and modify data, create aliases, etc, everything will depend on your imagination and of course, you want to read if you don't understand much.
7 .: In case it is not selected, simply write zsh and from there activate the changes with the source command, like this: