Access to the user API is only possible for users with a premium account. A user can only access their own user data. Authentication uses HTTP Basic. Use the TVmaze username as authentication username, and the TVmaze API key as authentication password. Your API key
curl \ -u "$API_USER:$API_PASS" \ https://api.tvmaze.com/v1/user/tags
curl \ -u "$API_USER:$API_PASS" \ https://api.tvmaze.com/v1/auth/validate
curl \ -u "$API_USER:$API_PASS" \ https://api.tvmaze.com/v1/user/episodes