diff --git a/README.md b/README.md
index d875931..9fb44a2 100644
--- a/README.md
+++ b/README.md
@@ -51,6 +51,16 @@ mydomain.com
 vpn.mydomain.com
 server.other-domain.net
 ```
+IMPORTANT: Secure your API keys! Since config.json contains sensitive credentials, restrict access to it so only the root user can read it:
+```
+sudo chown root:root /opt/ionos-ddns/config.json
+sudo chmod 600 /opt/ionos-ddns/config.json
+```
+
+Make script executable:
+```
+sudo chmod +x /opt/ionos-ddns/update_ddns.py
+```
 
 ### 4. Install System Service
 Copy the service file to systemd directory: