What you do is, go to Settings, then open Credentials. This page shows all the services you have already connected. Click on the specific credential you want to use, for example OpenAI or ElevenLabs. Once it opens, look at the browser address bar. The long string at the end of the URL is the credential ID. It usually looks like a random mix of letters and numbers. Copy that ID and paste it wherever Vapi asks for a credential ID, such as when creating or updating an assistant.