Unpack the archive relevant to your machine and place in $PATH

mkdir -p ~/.config/exercism
mv ../shell/exercism_completion.bash ~/.config/exercism/exercism_completion.bash

Load the completion in your .bashrc, .bash_profile or .profile by adding the following snippet:

if [ -f ~/.config/exercism/exercism_completion.bash ]; then
  source ~/.config/exercism/exercism_completion.bash
fi

Load up the completion by placing the exercism_completion.zsh somewhere on your $fpath as _exercism. For example:

mkdir -p ~/.zsh/functions
mv ../shell/exercism_completion.zsh ~/.zsh/functions/_exercism

and then add the directory to your $fpath in your .zshrc, .zsh_profile or .profile before running compinit:

export fpath=(~/.zsh/functions $fpath)
autoload -U compinit && compinit

If you are using the popular Oh My Zsh framework to manage your zsh plugins, you need to move the file exercism_completion.zsh to a new custom plugin:

mkdir -p $ZSH_CUSTOM/plugins/exercism
cp exercism_completion.zsh $ZSH_CUSTOM/plugins/exercism/_exercism

Then edit the file ~/.zshrc to include exercism in the list of plugins. Completions will be activated the next time you open a new shell. If the completions do not work, you should update Oh My Zsh to the latest version with omz update. Oh My Zsh now checks whether the plugin list has changed (more accurately, $fpath) and resets the zcompdump file.

Completions must go in the user defined $fish_complete_path. By default, this is ~/.config/fish/completions

mv ../shell/exercism.fish ~/.config/fish/exercism.fish