fix layout

wiki/pages/gemini-cgi.md

@@ -82,3 +82,13 @@ print(f"Hello {name}!")
 
 remember, anything that can read environment variables and write to stdout can 
 be used to make CGI, as long as the server can figure out how to execute it.
+
+##how to set a CGI script as executable
+
+The CGI script must be marked as executable in order to actually run. 
+
+To make the script executable, run this command:
+
+```
+chmod +x SCRIPT_NAME.cgi
+```