As a Blog Site owner or admin, go to Settings → Integrations → Writing model and billing and turn on Use my own AI keys.
Open OpenRouter if your key is from OpenRouter, or open Other AI providers and pick the service that issued it. Use that service’s setup link if needed. Enter the key only in its protected field and select Connect.
Under Models your team can use, select the writing models you want and save the provider’s models.
Select Only after my plan’s AI credits run out to use available credits first. If the next writing step costs more than your remaining balance, an eligible saved model can take over the entire step. For example, with two credits left and a more expensive draft, that draft uses your own key and the two credits remain. If there is no eligible key and model, the step can stop. To use your key now, leave the option unchecked and choose a model labeled for your key.
You do not need to send a key to anyone. For the full walkthrough, see connect your AI provider.