clarify activate command

backend/README.md

@@ -7,14 +7,16 @@
 2. Run the following commands inside the backend folder:
 ```
 python3 -m venv venv
-venv\Scripts\activate
+venv/Scripts/activate
 pip install -r requirements.txt
 python main.py
 ```
+
+If you are on Windows, run `venv\Scripts\activate` instead, for the second command.
 3. Go to `localhost:5000` in your web browser and you should see "Hello, World!".
 
 ## (Optional) Exercises
 
 - Install Postman (https://www.postman.com/downloads/) and use it make a request to this web server.
 - Add a new GET route at `/test` that shows "A new route".
-- Add a new POST route at `/post` that accepts a JSON body, and shows the `foo` key of the JSON.
+- Add a new POST route at `/post` that accepts a JSON body, and shows the `foo` key of the JSON.