If you use Vim 8 or later, the recommended way is using Vim's built-in package manager:
git clone https://github.com/udalov/kotlin-vim.git ~/.vim/pack/plugins/start/kotlin-vim
Plugin 'udalov/kotlin-vim'
to your ~/.vimrc
and run PluginInstall
.git clone https://github.com/udalov/kotlin-vim ~/.vim/bundle/kotlin-vim
mkdir -p ~/.vim/{syntax,indent,ftdetect,ftplugin}
cp syntax/kotlin.vim ~/.vim/syntax/kotlin.vim
cp indent/kotlin.vim ~/.vim/indent/kotlin.vim
cp ftdetect/kotlin.vim ~/.vim/ftdetect/kotlin.vim
cp ftplugin/kotlin.vim ~/.vim/ftplugin/kotlin.vim
cp -r syntax_checkers/kotlin ~/.vim/syntax_checkers/