To install Headline, download the headline.zsh-theme file and source it in your ~/.zshrc. To see your changes open a new shell (or re-source with . ~/.zshrc).
Clone the repository.
$ git clone https://github.com/moarram/headline.git
In your ~/.zshrc, source the headline.zsh-theme file in the repository.
source your/path/to/headline.zsh-theme
Instead of cloning the whole repository, only download the theme file.
$ wget https://raw.githubusercontent.com/moarram/headline/main/headline.zsh-theme
Source the theme as before.
Clone the repository into your themes directory.
$ git clone https://github.com/moarram/headline.git $ZSH_CUSTOM/themes/headline
Create a symlink to the theme (optional).
$ ln -s $ZSH_CUSTOM/themes/headline/headline.zsh-theme $ZSH_CUSTOM/themes/headline.zsh-theme
Set the theme in your ~/.zshrc with ZSH_THEME="headline" (or with ZSH_THEME="headline/headline" if you didn't symlink).
Add the following line to your ~/.zshrc.
antigen bundle moarram/headline@main