Update README

README.md

@@ -1,4 +1,5 @@
 # Trimage image compressor
+
 A cross-platform tool for optimizing PNG and JPG files.
 
 Trimage is a cross-platform GUI and command-line interface to optimize image files via [advpng](http://advancemame.sourceforge.net/comp-readme.html), [jpegoptim](http://www.kokkonen.net/tjko/projects.html), [optipng](http://optipng.sourceforge.net) and [pngcrush](https://pmt.sourceforge.io/pngcrush) depending on the
@@ -11,11 +12,23 @@ compressed on the highest available compression levels. Trimage gives you
 various input functions to fit your own workflow: a regular file dialog,
 dragging and dropping and various command line options.
 
-Visit [Trimage.org](http://trimage.org) for more information.
+## Installation instructions
 
-## Prerequisites
+Visit [Trimage.org](http://trimage.org) to install Trimage as a package.
 
+## Building instructions
+
+### Prerequisites
+
+- PyQt5
 - advpng
 - jpegoptim
 - optipng
 - pngcrush
+
+### Build from source
+
+Build and install by running:
+
+    python setup.py build
+    sudo python setup.py install