Added a description of dependencies and usage

README.md

@@ -1,3 +1,30 @@
-# pd-buddy-gtk
+# PD Buddy Configuration
 
-GTK+ GUI for PD Buddy Sink configuration
+PD Buddy Configuration is a GTK+ GUI for configuring PD Buddy Sink devices.
+
+## Dependencies
+
+PD Buddy Configuration is developed with these versions of its dependencies,
+but older versions may work.
+
+* GTK+ 3.22
+* Python 3.6
+* python-gobject 3.22
+* pyserial 3.2
+
+## Usage
+
+Plug your PD Buddy Sink(s) into your computer while holding the Setup button.
+Start PD Buddy Configuration with:
+
+    $ ./pd-buddy-gtk.py
+
+You will be greeted with a list of connected PD Buddy devices.  If there is
+more than one connected, you can identify them by clicking the light bulb
+button in each list entry (the selected device's LED will blink rapidly for two
+seconds).
+
+Click one of the list items to configure the device.  Select the desired
+voltage and current, then click Save.  If you want to configure other devices,
+click the Back arrow to return to the list.  After the settings have been
+saved, the devices can be safely disconnected at any time.