You need to install dependencies separately for the server and client side. To install, execute the following code snippets:
cd server; npm install; cd ..\client; npm install; cd ..
cd server && npm install && cd ../client && npm install && cd ..
All API Keys should be stored in server/apiKeys.env in the format
API_KEY=1234
ACCOMODATION_KEY=1234
BOOKING_KEY=1234
MONGODB_USER='username'
MONGODB_PASSWORD='password'
whereas 1234 is your API key for the specified API.
npm run server
npm run client