install vim plugins under vim8
$ mkdir -p ~/.vim/pack/plugins
$ cd ~/.vim/pack/plugins
$ git clone https://github.com/yuweijun/vundle.git start
$ cd start
$ git submodule update --init --recursive
install vim plugins under neovim
$ mkdir -p ~/.local/share/nvim/site/pack/plugins
$ cd ~/.local/share/nvim/site/pack/plugins
$ git clone https://github.com/yuweijun/vundle.git start
$ cd start
$ git submodule update --init --recursive
more infomation about packadd in vim8 and neovim
:h packages
:h packadd