diff --git a/README.md b/README.md
index a4435fc..abd25fe 100644
--- a/README.md
+++ b/README.md
@@ -7,7 +7,8 @@ This script is just a few lines added to upstream's `satnogs-client`
 
 
 # Use
-Install Python dependencies to your taste, such as:
+If you don't already have satnogs-client installed,
+install Python dependencies to your taste, such as:
 
 ```
 sudo apt update
@@ -18,8 +19,11 @@ pip install --user matplotlib numpy
 Change these two lines to your input data and output PNG:
 
 ```
-datafile_path='receiving_waterfall_.ogg'
-figure_path="waterfall.png"
+# Change this to your input file name
+datafile_path='receiving_waterfall_.dat'
+
+# This is the output PNG filename:
+figure_path='waterfall.png'
 ```
 
 Then run:
@@ -33,13 +37,16 @@ Then run:
 
 https://community.libre.space/t/creating-waterfall-images-from-satnogs-generated-dat-file/8479
 
+
 # Upstream
 
 * https://gitlab.com/librespacefoundation/satnogs/satnogs-client/
 
+
 # Status / Disclaimer
 I have no idea if this is doing what it should.
 
+
 # LICENSE
 Same as upstream, AGPLv3.
 
diff --git a/waterfall2png b/waterfall2png
index 6e0cdc1..fdc0c8c 100755
--- a/waterfall2png
+++ b/waterfall2png
@@ -1,4 +1,4 @@
-#!/usr/bin/python3
+#!/usr/bin/env python3
 
 import logging
 
@@ -9,8 +9,11 @@ matplotlib.use('Agg')
 
 import matplotlib.pyplot as plt  # isort:skip # noqa: E402 # pylint: disable=C0411,C0412,C0413
 
-datafile_path='receiving_waterfall_.ogg'
-figure_path="waterfall.png"
+# Change this to your input file name
+datafile_path='receiving_waterfall_.dat'
+
+# This is the output PNG filename:
+figure_path='waterfall.png'
 
 LOGGER = logging.getLogger(__name__)
 
@@ -151,4 +154,3 @@ class Waterfall():  # pylint: disable=R0903
 Waterfall.plot(Waterfall(datafile_path), figure_path=figure_path)
 
 print("Wrote file:", figure_path)
-