updated README

Author: nhartner

README.md

@@ -4,4 +4,94 @@
 
 PayID CLI for creating, fetching, signing and verifying PayIDs. Based on the Typescript PayID Utils library.
 
+## Prerequisites
 
+In order to use the CLI, both [node](https://nodejs.org/en/download/) and 
+[npm](https://docs.npmjs.com/downloading-and-installing-packages-locally) must be installed first. 
+
+## Installation
+
+To install the PayID CLI, run the command 
+```
+npm install -g @payid-org/payid-cli
+```
+
+## Interactive vs single command mode
+
+CLI can be run in interactive mode or as a single command mode. 
+In interactive mode, a prompt is shown where multiple commands can be run until the exit command is run.
+
+In single command mode, a single command is run and then the CLI exits. No prompt is shown in this mode.
+This mode is useful for running commands from a script, or from a shell where multiple commands can be
+chained together or to pipe output to another application. 
+
+To run the CLI in interactive mode, run ```payid```.
+
+To run the CLI in single command mode, run ```payid <command> <arguments>```. Example: 
+```
+payid load 'nhartner$xpring.money'
+```
+_note: when passing a PayID as an argument in single command mode, the PayID needs to be quoted 
+if run in a Linux shell (to avoid the '$' being interpolated as a variable by the Linux shell).
+
+## Commands
+
+A list of available commands can be found run running the `help` command.
+
+## Use Cases
+
+### Loading a PayID
+The following command can be used to load an existing PayID from a remote server:
+```
+load nhartner$xpring
+```
+This will fetch all the PayID address mappings for the given PayID from the remote
+server and displays the resulting JSON.
+
+### Creating a new PayID
+
+The following set of commands demonstrates how to create a new PayID, attach multiple
+address mappings and save the result to a JSON file.
+
+```
+init example$mypayid.com
+crypto-address add xrpl mainnet rP3t3JStqWPYd8H88WfBYh3v84qqYzbHQ6 12345
+crypto-address add btc mainnet 3M2CH71P6uZTra1PsjiEhNFB7kCENShCgt
+save
+```
+The end result should be a PayID json representation being saved to the local filesystem as
+example.json.
+
+### Identity Keys
+
+The PayID protocol supports signing address mappings using one or more cryptographic keys.
+The CLI provides several commands for generating and loading keys. Once a key is generated
+or loaded by the CLI, it is retained in the CLI's local storage for use in signing your PayID.
+Multiple identity keys can be generated or loaded using the `keys generate` and `keys load` commands.
+To remove all loaded keys from the CLI's local storage, use the `keys clear` command.
+The `keys list` command will show you all keys currently loaded into the CLI.
+
+To generate new key run:
+```
+keys generate
+```
+This will generate a new key and save it to a file named `identity-key.pem`. To load a previously
+created identity key, run `keys load </path/to/pem/file>`.
+
+### Signing a PayID
+
+In order to sign an PayID, it must either be loaded using the `load` command or created using the
+`init` command (as well as executing commands to add 1 or more addresses). Once a PayID has been
+initialized or loaded, it can be signed using an identity key (refer to the above section).
+
+Once your PayID has been loaded or initialized, and your identity key has been generated or loaded,
+you can sign the PayID using the command `sign`. This command will signed each of your PayID address
+mappings using the loaded identity keys and out the resulting PayID with verifiedAddress. The `save`
+command can be used to save your PayID, with signed addresses, to file.
+
+### Inspecting a Verified PayID
+
+Two commands are available to verify a PayID's verified addresses.
+
+- ```verify``` - checks if all the verified addresses have valid signatures
+- ```insepct``` - displays details information about each verified address and signatures.