mern-stack

First, you need to install npm package

npm install && npm install -D

Second,you need to go to your frontend folder

cd frontend && npm install

Third,you need to change your .env.example file to .env

PORT = 5000

MONGO_URI = mongodb://localhost:27017/yourdatabasename

JWT_SECRET = yourjwtsecret

NODE_ENV = development or production

PAYPAL_CLIENT_ID = Your paypal Client Id

To Learn more about paypal client

PayPal Client