docs: add OpenAI API key setup instructions in README

README.md

@@ -13,4 +13,12 @@ hf_oauth_expiration_minutes: 480
 short_description: Agent for the final hands-on assignment of the Agents course
 ---
 
-Check out the configuration reference at https://huggingface.co/docs/hub/spaces-config-reference
+## Requirements
+
+To run this project, you need to have an OpenAI API key. Set your `OPENAI_API_KEY` as an environment variable:
+
+```bash
+export OPENAI_API_KEY='your-api-key'
+```
+
+You can get your OpenAI API key from [here](https://platform.openai.com/account/api-keys).