Update the README.md (#3)

Author: giarc3

README.md

@@ -1,3 +1,74 @@
 # IronOxide CLI
 
 Command-line interface for IronOxide functions to create users, devices, and groups.
+
+## Configuration
+
+To use the IronOxide CLI, you must first obtain an Identity Assertion Key file and a configuration file
+from the [IronCore Labs Admin Console](https://admin.ironcorelabs.com).
+
+### Identity Assertion Key File
+
+An Identity Assertion Key file must be downloaded from the admin console interface immediately after creating
+a new Identity Assertion Key. To use IronOxide CLI's defaults, it should be named `assertionKey.pem`.
+
+### IronCore Config File
+
+An IronCore Config file can be downloaded from the admin console on creation of the very first project. For subsequent projects, it will need to be created manually. The file is of the form:
+
+```javascript
+{
+  "projectId": YOUR_PROJECT_ID,
+  "segmentId": "YOUR_SEGMENT_ID",
+  "identityAssertionKeyId": YOUR_IDENTITY_ASSERION_KEY_ID
+}
+```
+
+Note that key names are case sensitive.
+
+To use IronOxide CLI's defaults, it should be named `config.json`.
+
+## Installation
+
+IronOxide CLI requires Rust to be installed in order to compile the binary for your architecture.
+For information on installing Rust, visit https://www.rust-lang.org/tools/install.
+
+Once Rust is installed, it can be used to download, compile, and install the IronOxide CLI binary with the command
+
+```
+cargo install --git https://github.com/IronCoreLabs/ironoxide-cli
+```
+
+## Usage
+
+IronOxide CLI must be run from the directory where your Identity Assertion Key and configuration files are.
+It is used by running `ironoxide-cli`, followed by your desired subcommands and options.
+You can see all the available subcommands by running `ironoxide-cli -h`.
+There are currently two subcommands available: `user-create` and `group-create`.
+
+### User and Device Creation
+
+The `user-create` subcommand is used to create a user in the IronCore service,
+generate a device for that user, and output the device context to a file.
+It requires the desired user's ID and password. The user's device context will be output to a file named "\<USER-ID\>.json".
+
+### Group Creation
+
+The `group-create` subcommand is used to create multiple groups for the given user.
+As it requires the user's device context in a file named "\<USER-ID.json\>", it is typically run
+immediately after `user-create`. The group will be created with the given user as the owner and with no additional administrators or members.
+
+## Examples
+
+```console
+$ ironoxide-cli user-create ironadmin -p foobar
+Creating user "ironadmin"
+Generating device for user "ironadmin"
+Outputting device context to "ironadmin.json"
+
+$ ironoxide-cli group-create customers employees others -u ironadmin
+Found DeviceContext in "ironadmin.json"
+Generating group "employees" for user "ironadmin"
+Generating group "customers" for user "ironadmin"
+Generating group "others" for user "ironadmin"
+```