Add usage instructions

README.md

@@ -1,4 +1,33 @@
 # devenv
 
-Your shell and dev environment, containerized.
+ZSH and NeoVim environment, containerized.
+
+## Usage
+
+Begin by cloning this repo
+
+    git clone https://github.com/joshwbrick/devenv.git
+    cd devenv
+
+Copy the example `env` file to the path `.env`. The edit the file to contain the desired values.
+
+    cp env.example .env
+    nvim .env
+
+Add your dotfiles to the `dotfiles/` directory. You can checkout another repo directly in that directory. For example:
+
+    cd dotfiles
+    git clone https://github.com/user/dotfiles.git
+
+Run the build and docker will begin creating the image using your environment variables.
+
+    make build
+
+If they do not exist this will create three required files in the `dotfiles` directory. The required files are called `setup.sh`,
+`init.vim` and `zshrc` and must be in the root of the `dotfiles` directory. You may include any other files or directories as well.
+These will be made available in the container at `~/all_dotfiles`.
+
+`setup.sh` can contain any shell code to install or setup your peronsal shell or vim environment. For example, in mine I
+install vim-plug and setup a PHP 8 development environment. `init.vim` should contain your vim config and `zshrc` should contain
+setup for zsh like your personal environment variables, aliases, functions, etc.