Add langauge about tabs being open

module3/lessons/intro_to_cypress_prework.md

@@ -194,6 +194,13 @@ Next, we need to add a script to our `package.json` file to run Cypress.
     }
   }
 ```
+
+**Important!** You'll need three tabs open:  
+1. A tab with your react app running (react-ideabox: `npm start`)  
+2. A tab with your backend running (ideabox-api: `node server.js`)  
+3. A tab with cypress running (react-ideabox: `npm run cypress`)  
+ALL THREE TABS NEED TO BE ACTIVE FOR CYPRESS TO WORK!
+
 Now it's time to run Cypress. 
 ```bash
 npm run cypress