update readme with better docs

README.md

 # `fsljs`
 
-## Usage
+This is the `fsljs` JavaScript library. It contains helper functions and facilitates interaction between the [`fsl-desktop`](https://git.fmrib.ox.ac.uk/fsl/gui/desktop) electron app and the FSL React web-based [GUIs](https://git.fmrib.ox.ac.uk/fsl/gui).
+
+# Development
+
+## Prerequisites
+
+It is assumed that your development machine is either a Mac or Linux machine.
+
+- [nodejs and NPM](https://nodejs.org/en/)
+
+## Setup
+
+Clone and cd into this repo
+
+```bash
+git clone https://git.fmrib.ox.ac.uk/fsl/gui/fsljs.git
+
+cd fsljs
+```
+
+Install dependencies via npm
+
+```bash
+npm install
+```
+
+## Publishing
+
+Publishing is a manual process until the proper CI/CD pipeline is in place. To publish, run the following command:
+
+```bash
+npm run pub
+```