Add more details to the readme

Author: seancdavis

README.md

@@ -1,3 +1,48 @@
 # create-stackbit-app
 
 Run `npx create-stackbit-app` in your terminal to create a new Stackbit application or add Stackbit into an existing site.
+
+## Usage
+
+To create a new Stackbit project from a starter, run the following command:
+
+```txt
+npx create-stackbit-app [dir]
+```
+
+To see a full list of options use the `--help` flag:
+
+```txt
+> npx create-stackbit-app --help
+
+Options:
+      --version  Show version number                                   [boolean]
+  -s, --starter  Choose a starter           [choices: "nextjs", "ts-mui-nextjs"]
+      --help     Show help                                             [boolean]
+```
+
+### Choosing a Starter
+
+Use the `--starter` option for specifying a starter. Run the command with the `--help` flag to see a full list of available starters.
+
+```txt
+npx create-stackbit-app --starter ts-mui-nextjs
+```
+
+If no starter option is provided, [the default starter](https://github.com/stackbit-themes/nextjs-starter) is used.
+
+### Setting Project Directory
+
+Pass a directory name as the only argument when running the command. For example, if you wanted your directory to be name `my-site`, the command would look something like this:
+
+```txt
+npx create-stackbit-app my-site
+```
+
+If no name is provided, the directory will be `my-stackbit-site-[id]`, where `[id]` is a randomly-generated string used to avoid directory conflicts.
+
+## Adding Stackbit to Existing Projects
+
+The script detects when you may be working with an existing project (it looks for a `package.json` file in the working directory).
+
+If in an existing project, the script asks if you'd like to add Stackbit to the project. Today, this only prints a resource URL. If you choose _no_, the command exits.