Update installation instructions

README.md

@@ -5,11 +5,20 @@ https://realtimedata.waternsw.com.au
 
 ## Installation ##
 
+1. Install `waternsw-grabber`
+
 ```
 pip install git+http://git.wrl.unsw.edu.au:3000/danh/waternsw-grabber.git
 ```
 
-Firefox is required (ww.firefox.com),
+2. Install `Firefox`  
+https://www.mozilla.org/en-GB/firefox/
+
+3. Download the Mozilla `geckodriver`  
+https://github.com/mozilla/geckodriver/releases
+
+4. Ensure `geckodriver` is in your system search path  
+(the easiest way is to keep the executable in your working directory)
 
 ## Usage ##