diff --git a/README.md b/README.md
index 0918d93e..e230ee42 100644
--- a/README.md
+++ b/README.md
@@ -94,6 +94,12 @@ const { calldata, value } = SwapRouter.swapCallParameters([unwrapWETH, seaportTr
 
 
 ## Running this package
+Create `.env` file with forking url
+
+```
+FORK_URL='xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx'
+```
+
 Make sure you are running `node v16`
 Install dependencies and run typescript unit tests
 ```bash