Update CONTRIBUTING.md

update contributing docs

CONTRIBUTING.md

@@ -3,7 +3,7 @@
 ## Pull Requests
 We actively welcome your pull requests.
 
-1. Fork the repo and create your branch from `main`.
+1. Fork the repo and create your branch from `master`.
 2. Update the documentation if necessary.
 3. Make sure your code lints with `black`.
 
@@ -13,10 +13,19 @@ Clone the repo & install the development requirements:
 git clone https://github.com/banditml/offline-policy-evaluation.git
 ```
 
+```
+cd offline-policy-evaluation
+virtualenv env
+. env/bin/activate
+pip install -r dev-requirements.txt
+```
+
+To test changes to the library, run the notebooks in `examples/` which use the local version of the library.
+
 ## Issues
 We use GitHub issues to track public bugs. Please ensure your description is
 clear and has sufficient instructions to be able to reproduce the issue.
 
 ## License
 By contributing to banditml/offline-policy-evaluation, you agree that your
-contributions will be licensed under the COPYING file in the root directory of this source tree.
+contributions will be licensed under the COPYING file in the root directory of this source tree.