Install Packer first:
git clone --depth 1 https://github.com/wbthomason/packer.nvim \
~/.local/share/nvim/site/pack/packer/start/packer.nvim
Then clone the Dracula theme for oh-my-zsh:
git clone https://github.com/dracula/zsh.git \
~/.local/share/zsh/themes/dracula