Simply go to http://randomkeygen.com/ and generate a random key. You can select between a wide selection of encryption keys. I would recommend going with at least a 128-bit wep key.
128-bit encryption will provide a sufficient security for our server (unless someone else can chime in). Go to your /etc/openhab/webapps/static folder and create a new file called “secret”.
Paste your secret key into the “secret” file.
As for whether your addon is loaded, I dont know…