updated docs

docs/description.rst

@@ -10,6 +10,17 @@ CoderGPT is a command line interface for generating/modifying code. It allows de
 enhance code by commenting, optimizing, documenting and adding tests to their projects using 
 the power of LLM and GPT. This project is powered by `langchain <https://github.com/langchain-ai/langchain>`_.
 
+.. note::
+   **NOTE**
+   Before using CoderGPT, ensure that the environment variable ``OPENAI_API_KEY`` is set locally on your machine. This key is required for authentication with the OpenAI API which powers the underlying language model.
+
+   .. code-block:: sh
+
+      export OPENAI_API_KEY='your-api-key-here'
+
+   Replace ``your-api-key-here`` with your actual OpenAI API key. This step is crucial for the proper functioning of CoderGPT as it relies on the OpenAI API for generating and modifying code.
+
+
 Installation
 ------------