3 options:
1, use REST UI:
Make sure you have the REST UI installed (it’s an add-on), then go to the REST UI, and set the state:
http://demo.openhab.org:8080/doc/index.html
2, REST CURL
3, use CLI (command line interface):
http://docs.openhab.org/administration/console.html
command is:
smarthome:update spotify_client_id {your_id}
Hope this helps!