diff --git a/README.md b/README.md
index f2a1890..5da177a 100644
--- a/README.md
+++ b/README.md
@@ -2,6 +2,25 @@
 
 Update DNS records with your current external IP address using the netcup DNS API.
 
+## Configuration
+
+For each netcup customer, create a `.ini` configuration file. Here is an example:
+
+```ini
+[credentials]
+customer = 123456
+api_key = abcdefghijklmnopqrstuvwxyz
+api_password = abcdefghijklmnopqrstuvwxyz
+
+[example.com]
+hostname = @
+type = A
+
+[foo.bar]
+hostname = @
+type = A
+```
+
 ## TODOs
 
 Alternative external IP detection: