diff --git a/README.md b/README.md
index 15daefa..3fcc405 100644
--- a/README.md
+++ b/README.md
@@ -31,4 +31,12 @@ simulations on parallel compute hardware (mainly GPUs).
 You can install the requirements and their dependencies easily with
 ```bash
 pip intall -r requirements.txt
+```
+
+## Running
+The root directory contains ``fdtd.py``, which sets up and runs a sample simulation
+ (cavity ringdown).
+
+```bash
+python3 fdtd.py
 ```
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