First, you need to collect API Key from OpenAI website, please check this FAQ tutorial to learn the process:
https://support.marketro.com/a/solutions/articles/13000101286?portalId=13000000343
1. After login to AI Prompt Ace, go to your profile page -
2. Click Update Profile
3. Insert your OpenAI API/Secret Key and Click update
Here is video explaining more: