Update README

tikz/gpx-gps-elevation-chart-generator/README.md

@@ -1,3 +1,7 @@
 Compiled example
 ----------------
 ![Example](elevation-chart.png)
+
+
+Run `python elevation_chart_gen.py -f ../Downloads/Jul_3,_2016_12_52_51.gpx` to
+generate the `data.csv`. Then run `make` to generate the chart.