diff --git a/readme.md b/readme.md
index 7dd8250..b309599 100644
--- a/readme.md
+++ b/readme.md
@@ -7,8 +7,16 @@ Also check [its tweet thread](https://twitter.com/ShunyuYao12/status/16593575474
 ## Setup
 You need to first have an OpenAI API key and store it in the environment variable ``OPENAI_API_KEY`` (see [here](https://help.openai.com/en/articles/5112595-best-practices-for-api-key-safety)).
 
+If you use custom base url, set it by environment variable ``OPENAI_API_BASE`` (e.g. "https://api.openai.com/v1")
+
+Note GPT-4 model is farily slow, please be patient
+
 Package requirement: ``openai``, ``backoff``, ``sympy``, ``numpy``. 
 
+```
+pip install openai backoff sympy numpy
+```
+
 
 ## Experiments