diff --git a/README.md b/README.md
index 40beee5..7b06d4d 100644
--- a/README.md
+++ b/README.md
@@ -15,9 +15,11 @@ This crate is structured as a library; main.rs is just a glorified test harness
 shows an example of using the library to render a scene. It uses SDL2 to display the
 rendered image.
 
-On Ubuntu 19.04, if you have the libsdl2-dev package installed you should be able to
-run "cargo run" and see a window with a test scene rendered into it. In theory it should
-work on any platform with SDL2 installed but I've only tested it on Ubuntu Linux.
+On Ubuntu 19.04, if you have the libsdl2-dev package installed you
+should be able to run `cargo run --release -- --size 800 600` and see
+a window with a test scene rendered into it. In theory it should work
+on any platform with SDL2 installed but I've only tested it on Ubuntu
+Linux.
 
 ![](.github/output3.png?raw=true "Test Image 3")
 ![](.github/output.png?raw=true "Test Image 1")